U.S. patent application number 10/093516 was filed with the patent office on 2002-09-19 for communication network, path setting method and recording medium having path setting program recorded thereon.
Invention is credited to Suemura, Yoshihiko.
Application Number | 20020131424 10/093516 |
Document ID | / |
Family ID | 18929097 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020131424 |
Kind Code |
A1 |
Suemura, Yoshihiko |
September 19, 2002 |
Communication network, path setting method and recording medium
having path setting program recorded thereon
Abstract
To prevent load of route calculation from being centralized in
part of units. A node calculates routes of a primary path and an
alternate path and sends them to a management center. The
management center checks whether SRLGs of the two routes overlap,
and instructs the node to perform calculation again if the routes
overlap. The management center searches for an alternate path
having a route overlapping the route of the above described
alternate path. When an overlapping alternate path exists, and
SRLGs of a primary path corresponding to the alternate path and the
above described primary path do not overlap, a link is shared in an
overlapping portion of the routes of the two alternate paths.
Inventors: |
Suemura, Yoshihiko; (Tokyo,
JP) |
Correspondence
Address: |
STEVEN I. WEISBURD, ESQ.
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
1177 AVENUE OF THE AMERICAS
41st FLOOR
NEW YORK
NY
10036-2714
US
|
Family ID: |
18929097 |
Appl. No.: |
10/093516 |
Filed: |
March 11, 2002 |
Current U.S.
Class: |
370/400 ;
370/228 |
Current CPC
Class: |
H04L 45/24 20130101;
H04L 45/28 20130101; H04L 41/12 20130101; H04L 45/22 20130101; H04L
45/00 20130101 |
Class at
Publication: |
370/400 ;
370/228 |
International
Class: |
H04L 012/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2001 |
JP |
071365/2001 |
Claims
What is claimed is:
1. A communication network comprising: a plurality of nodes
constituting a network; and a management center connected to each
of said nodes, wherein each of said nodes has topology information
of said network, and said management center has information on a
risk sharing resource group.
2. A communication network comprising: a plurality of nodes
constituting a network; and a management center connected to each
of said nodes, wherein each of said nodes has topology information
of said network, and said management center has currently set path
information.
3. A communication network comprising: a plurality of nodes
constituting a network; and a management center connected to each
of said nodes, wherein each of said nodes has topology information
of said network, and said management center has information on a
risk sharing resource group and currently set path information.
4. A communication network comprising: a plurality of nodes
constituting a network; and a management center connected to each
of said nodes, wherein each of said nodes has topology information
of said network and information on a risk sharing resource group,
and said management center has currently set path information.
5. A communication network comprising: a plurality of nodes
constituting a network, wherein each of said nodes has topology
information of said network, information on a risk sharing resource
group, and information on a currently set path passing the node
itself.
6. A communication network in which a communication network as set
forth in claim 3 consists of a plurality of subnetworks, wherein
each of nodes comprises an external routing table showing a
boundary node that a route passes when a path to a destination node
in another subnetwork is set.
7. A communication network in which a communication network as set
forth in claim 5 consists of a plurality of subnetworks, wherein
each of nodes comprises an external routing table showing a
boundary node that a route passes when a path to a destination node
in another subnetwork is set.
8. The communication network according to claim 1, wherein when a
first path and a second path having different routes are
calculated, said information on the risk sharing resource group is
referred, and paths having no overlapping risk sharing resource
group are determined.
9. The communication network according to claim 2, wherein when a
plurality of pairs of first paths and second paths having different
routes are calculated, said path information is referred, and a
plurality of said second paths having an overlapping route is
searched.
10. The communication network according to claim 9, wherein when
said second paths having the overlapping route exist, said
information on the risk sharing resource group is referred, and it
is checked whether the first paths pairing up with said respective
second paths have an overlapping risk sharing resource group.
11. The communication network according to claim 10, wherein each
of said nodes are linked by a link group consisting of one or more
links, and when the first paths pairing up with said respective
second path have no overlapping risk sharing resource group, said
plurality of second paths having the overlapping route share a link
on said link group.
12. The communication network according to claim 10, wherein each
of said nodes are linked by a link group consisting of a plurality
of links, and when the first paths pairing up with said respective
second path have an overlapping risk sharing resource group, said
plurality of second paths having the overlapping route share no
link on said link group.
13. The communication network according to claim 8, wherein said
first path is a primary path, and said second path is an alternate
path.
14. A management center connected to a plurality of nodes
constituting a network, wherein said management center has
information on a risk sharing resource group, and when each of said
nodes calculates a first path and a second path having different
routes, the management center sends said information on the risk
sharing resource group to said node.
15. A management center connected to a plurality of nodes
constituting a network, wherein said management center has
currently set path information, and when each of said nodes
calculates a first path and a second path having different routes,
the management center refers to said path information to check
whether an already set second path overlapping the second path
calculated by said node exists.
16. The management center according to claim 14 connected to the
plurality of nodes constituting the network, wherein said
management center has said information on the risk sharing resource
group and said path information.
17. A node constituting a network, wherein said node has topology
information of said network, and when calculating a first path and
a second path having different routes, said node obtains
information on a risk sharing resource group from a management
center connected to said node.
18. A node constituting a network, wherein said node has topology
information of said network, and when said node calculates a first
path and a second path having different routes, a management center
connected to said node refers to currently set path information to
check whether an already set second path overlapping the second
path calculated by said node exists.
19. The node according to claim 17 constituting the network,
wherein said node has the topology information of said network, and
the management center connected to said node has said information
on the risk sharing resource group and said path information.
20. A node constituting a network, wherein said node has topology
information of said network and information on a risk sharing
resource group, and when said node calculates a first path and a
second path having different routes, a management center connected
to said node refers to currently set path information to check
whether an already set second path overlapping the second path
calculated by said node exists.
21. A node constituting a network, wherein said node has topology
information of said network, information on a risk sharing resource
group, and information on a currently set path passing the node
itself, and when calculating a first path and a second path having
different routes, said node refers to these information.
22. A node in a communication network in which a communication
network as set forth in claim 19 consists of a plurality of
subnetworks, wherein each of said nodes has topology information of
said network, and comprises an external routing table showing a
boundary node that a route passes when a path to a destination node
in another subnetwork is set.
23. A node in a communication network in which a communication
network as set forth in claim 21 consists of a plurality of
subnetworks, wherein each of said nodes has topology information of
said network, information on a risk sharing resource group, and
currently set path information, and comprises an external routing
table showing a boundary node that a route passes when a path to a
destination node in another subnetwork is set.
24. A path setting method in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has information on a risk sharing resource group, and said method
comprises: a first step in which a source node refers to said
topology information of the network to calculate a route of a first
path and send the route obtained to said management center; a
second step in which said management center refers to said
information on the risk sharing resource group to return a list of
a link group not belonging to said risk sharing resource group that
the route sent from said source node passes to said source node;
and a third step in which said source node refers to the list sent
from said management center to calculate a route of a second
path.
25. A path setting method in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has path information, and said method comprises: a first step in
which a source node refers to said topology information of the
network to calculate routes of a first path and a second path and
send the routes obtained to said management center; and a second
step in which said management center refers to said path
information to search for an existing second path having a route
overlapping the route of said second path.
26. The path setting method according to claim 25, further
comprising a third step in which when it is determined in said
second step that an already set second path having a route
overlapping the route of said second path exists, said management
center sends a message that a link can be shared in an overlapping
link group to said source node when said second path is set.
27. The path setting method according to claim 25, further
comprising a fourth step in which when it is determined in said
second step that an already set second path having a route
overlapping the route of said second path does not exist, said
management center sends a message that a link can not be shared in
an overlapping link group to said source node when said second path
is set.
28. A path setting method in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has information on a risk sharing resource group and currently set
path information, and said method comprises: a first step in which
a source node refers to said topology information of the network to
calculate routes of a first path and a second path and send the
routes obtained to said management center; a second step in which
said management center refers to said information on the risk
sharing resource group to check risk sharing resource groups that
the routes of said first path and said second path sent from said
source node pass; and a third step in which when it is determined
in said second step that said risk sharing resource groups do not
overlap, said management center refers to said path information to
search for an already set second path having a route overlapping
the route of said second path.
29. The path setting method according to claim 28, further
comprising a fourth step in which when an already set second path
having a route overlapping the route of said second path exists in
said third step, said risk sharing resource groups that the route
of the first path corresponding to said second path and a route of
a first path corresponding to said already set second path pass are
checked.
30. The path setting method according to claim 29, further
comprising a fifth step in which when it is determined in said
fourth step that said risk sharing resource groups of both of the
first paths do not overlap, said management center sends a message
that a link can be shared in an overlapping link group to said
source node when said second path is set.
31. The path setting method according to claim 29, further
comprising a sixth step in which when it is determined in said
fourth step that said risk sharing resource groups of both of the
first paths overlap, said management center sends a message that a
link can not be shared in an overlapping link group to said source
node when said second path is set.
32. A path setting method in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has information on a risk sharing resource group and currently set
path information, and said method comprises: a first step in which
a source node refers to said topology information of the network to
calculate a route of a first path and send the route obtained to
said management center; a second step in which said management
center refers to said information on the risk sharing resource
group to return a list of a link group not belonging to said risk
sharing resource group that the route sent from said source node
passes to said source node; a third step in which said source node
refers to the list sent from said management center to calculate a
route of a second path and send the route obtained to said
management center; and a fourth step in which said management
center refers to said path information to search for an already set
second path having a route overlapping the route of said second
path.
33. The path setting method according to claim 32, further
comprising a fifth step in which when an already set second path
having a route overlapping the route of said second path exists in
said fourth step, said risk sharing resource groups that the route
of the first path corresponding to said second path and a route of
a first path corresponding to said already set second path pass are
checked.
34. The path setting method according to claim 33, further
comprising a sixth step in which when it is determined in said
fifth step that said risk sharing resource groups of both of the
first paths do not overlap, said management center sends a message
that a link can be shared in an overlapping link group to said
source node when said second path is set.
35. The path setting method according to claim 33, further
comprising a seventh step in which when it is determined in said
fifth step that said risk sharing resource groups of both of the
first paths overlap, said management center sends a message that a
link can not be shared in an overlapping link group to said source
node when said second path is set.
36. A path setting method in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network and information on a risk
sharing resource group, and said management center has currently
set path information, and said method comprises: a first step in
which a source node refers to said topology information of the
network and said information on the risk sharing resource group to
calculate routes of a first path and a second path so as not to
pass the same risk sharing resource group; a second step in which
said source node sends the routes calculated and obtained to said
management center; and a third step in which said management center
refers to said path information to search for an already set second
path having a route overlapping the route of said second path.
37. The path setting method according to claim 36, further
comprising a fourth step in which when an already set second path
having a route overlapping the route of said second path exists in
said third step, said risk sharing resource groups that the route
of the first path corresponding to said second path and a route of
a first path corresponding to said already set second path pass are
checked.
38. The path setting method according to claim 37, further
comprising a fifth step in which when it is determined in said
fourth step that said risk sharing resource groups of both of the
first paths do not overlap, said management center sends a message
that a link can be shared in an overlapping link group to said
source node when said second path is set.
39. A path setting method in a communication network comprising a
plurality of nodes constituting a network, wherein each of said
nodes has topology information of said network, information on a
risk sharing resource group, and information on a currently set
path passing the node itself, and said method comprises: a first
step in which a source node refers to said topology information of
the network and said information on the risk sharing resource group
to calculate routes of a first path and a second path so as not to
pass the same risk sharing resource group; and a second step in
which each node on said routes receives a signal from an upstream
node, refers to said information on the risk sharing resource group
and said information on the currently set path passing the node
itself to detect a second path having an overlapping route in a
link group between the node itself and a downstream node and
compare said risk sharing resource groups of said first path.
40. A path setting method in a communication network in which a
communication network as set forth in claims 32 consists of a
plurality of subnetworks, wherein each of said nodes comprises an
external routing table showing a boundary node that a route passes
when a path to a destination node in another subnetwork is set, and
said method comprises: a ninth step in which a first path and a
second path from a source node to said boundary node are set; and a
tenth step in which a first path and a second path from said
boundary node to a destination node in another subnetwork are
set.
41. A path setting method in a communication network in which a
communication network as set forth in claim 39 consists of a
plurality of subnetworks, wherein each of said node comprises an
external routing table showing a boundary node that a route passes
when a path to a destination node in another subnetwork is set, and
said method comprises: a third step in which a first path and a
second path from a source node to said boundary node are set; and a
fourth step in which a first path and a second path from said
boundary node to a destination node in another subnetwork are
set.
42. The path setting method according to claim 24, wherein said
first path is a primary path, and set second path is an alternate
path.
43. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of the nodes, wherein each of the nodes has
topology information of the network, and the management center has
information on a risk sharing resource group, and said path setting
program comprises: a first step in which a source node refers to
said topology information of the network to calculate a route of a
first path and send the route obtained to said management center,
and a second step in which said management center refers to said
information on the risk sharing resource group to return a list of
a link group not belonging to said risk sharing resource group that
the route sent from said source node passes to said source node,
and then said source node refers to the list sent from said
management center to calculate a route of a second path.
44. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has path information, and said path setting program comprises a
first step in which a source node refers to said topology
information of the network to calculate routes of a first path and
a second path and send the routes obtained to said management
center, and said management center refers to said path information
to search for an existing second path having a route overlapping
the route of said second path.
45. The recording medium according to claim 44, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that an already
set second path having a route overlapping the route of said second
path exists, said management center sends a message that a link can
be shared in an overlapping link group to said source node when
said second path is set, and then a link allocated to the already
set second path having the route overlapping the route of said
second path is allocated in said link group.
46. The recording medium according to claim 44, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that an already
set second path having a route overlapping the route of said second
path does not exist, said management center sends a message that a
link can not be shared in an overlapping link group to said source
node when said second path is set, and then a link other than a
link allocated to the already set second path having the route
overlapping the route of said second path is allocated in said link
group.
47. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network, and said management center
has information on a risk sharing resource group and currently set
path information, said path setting program comprises a first step
in which a source node refers to said topology information of the
network to calculate routes of a first path and a second path and
send the routes obtained to said management center, and said
management center refers to said information on the risk sharing
resource group to check risk sharing resource groups that the
routes of said first path and said second path sent from said
source node passes, and when it is determined that said risk
sharing resource groups do not overlap, said management center
refers to said path information to search for an already set second
path having a route overlapping the route of said second path.
48. The recording medium according to claim 47, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when an already set second path
having a route overlapping the route of said second path exists,
said risk sharing resource groups that the route of the first path
corresponding to said second path and a route of a first path
corresponding to said already set second path pass are checked.
49. The recording medium according to claim 48, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that said risk
sharing resource groups of both of said first paths do not overlap,
said management center sends a message that a link can be shared in
an overlapping link group to said source node when said second path
is set, and then a link allocated to an already set second path
having a route overlapping the route of said second path is
allocated in said link group.
50. The recording medium according to claim 48, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that said risk
sharing resource groups of both of said first paths overlap, said
management center sends a message that a link can not be shared in
an overlapping link group to said source node when said second path
is set, and then a link other than a link allocated to an already
set second path having a route overlapping the route of said second
path is allocated in said link group.
51. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of the nodes, wherein each of said nodes has
topology information of said network, and said management center
has information on a risk sharing resource group and currently set
path information, and said path setting program comprises: a first
step in which a source node refers to said topology information of
the network to calculate a route of a first path and send the route
obtained to said management center; and a second step in which said
management center refers to said information on the risk sharing
resource group to return a list of a link group not belonging to
said risk sharing resource group that the route sent from said
source node passes to said source node, and then said source node
refers to the list sent from said management center to calculate a
route of a second path and send the route obtained to said
management center, and said management center refers to said path
information to search for an already set second path having a route
overlapping the route of said second path.
52. The recording medium according to claim 51, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when an already set second path
having a route overlapping the route of said second path exists,
said risk sharing resource groups that the route of the first path
corresponding to said second path and a route of a first path
corresponding to said already set second path pass are checked.
53. The recording medium according to claim 52, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that said risk
sharing resource groups of both of said first paths do not overlap,
said management center sends a message that a link is shared in an
overlapping link group to said source node when said second path is
set, and then a link allocated to an already set second path having
a route overlapping the route of said second path is allocated in
said link group.
54. The recording medium according to claim 52, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that said risk
sharing resource groups of both of said first paths overlap, said
management center sends a message that a link can not be shared in
an overlapping link group to said source node when said second path
is set, and then a link other than a link allocated to an already
set second path having a route overlapping the route of said second
path is allocated in said link group.
55. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network and a management center
connected to each of said nodes, wherein each of said nodes has
topology information of said network and information on a risk
sharing resource group, and said management center has currently
set path information, and said path setting program comprises: a
first step in which a source node refers to said topology
information of the network and said information on the risk sharing
resource group to calculate routes of a first path and a second
path so as not to pass the same risk sharing resource group; and a
second step in which said source node sends the routes calculated
and obtained to said management center, and said management center
refers to said path information to search for an already set second
path having a route overlapping the route of said second path.
56. The recording medium according to claim 55, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when an already set second path
having a route overlapping the route of said second path exists,
said risk sharing resource group that the route of the first path
corresponding to said second path and a route of a first path
corresponding to said already set second path pass are checked.
57. The recording medium according to claim 56, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that when it is determined that said risk
sharing resource groups do not overlap, said management center
sends a message that a link can be shared in an overlapping link
group to said source node when said second path is set, and then a
link allocated to an already set second path having a route
overlapping the route of said second path is allocated in said link
group.
58. A recording medium storing a path setting program for
controlling a node in a communication network comprising a
plurality of nodes constituting a network, wherein each of said
nodes has topology information of said network, information on a
risk sharing resource group, and information on a currently set
path passing the node itself, and said path setting program
comprises: a first step in which a source node refers to said
topology information of the network and said information on the
risk sharing resource group to calculate routes of a first path and
a second path so as not to pass the same risk sharing resource
group; and a second step in which each node on said routes receives
a signal from an upstream node, refers to said information on the
risk sharing resource group and said information on the currently
set path passing the node itself to detect a second path having an
overlapping route in a link group between the node itself and a
downstream node and compare said risk sharing resource groups of
said first path.
59. A recording medium storing a path setting program for
controlling a node in a communication network consisting of a
plurality of subnetworks, said subnetworks are networks defined in
claim 51, wherein each of said nodes comprises an external routing
table showing a boundary node that a route passes when a path to a
destination node in another subnetwork is set, and said path
setting program comprises: a third step in which a first path and a
second path from a source node to said boundary node are set; and a
fourth step in which a first path and a second path from said
boundary node to a destination node in another subnetwork are
set.
60. A recording medium storing a path setting program for
controlling a node in a communication network consisting of a
plurality of subnetworks, said subnetworks are networks defined in
claim 58, wherein each of said node comprises an external routing
table showing a boundary node that a route passes when a path to a
destination node in another subnetwork is set, and said path
setting program comprises: a third step in which a first path and a
second path from a source node to said boundary node are set; and a
fourth step in which a first path and a second path from said
boundary node to a destination node in another subnetwork are
set.
61. The recording medium according to claim 43, storing said path
setting program for controlling a node, wherein said path setting
program is designed such that said first path is a primary path,
and set second path is an alternate path.
62. A recording medium having a path setting program recorded
thereon for a management center in a communication network
comprising a plurality of nodes constituting a network and a
management center connected to each of the nodes, wherein each of
said nodes has topology information of the network, and said
management center has information on a risk sharing resource group,
said medium comprises a first step in which a source node refers to
said topology information of the network to calculate a route of a
first path and send the route obtained to said management center,
and then said management center refers to said information on the
risk sharing resource group to return a list of a link group not
belonging to said risk sharing resource group that the route sent
from said source node passes to said source node, and said source
node refers to the list sent from said management center to
calculate a route of a second path.
63. A recording medium having a path setting program recorded
thereon for a management center in a communication network
comprising a plurality of nodes constituting a network and a
management center connected to each of said nodes, wherein each of
said nodes has topology information of said network, and said
management center has path information, and said path setting
program comprises a first step in which a source node refers to
said topology information of the network to calculate routes of a
first path and a second path and send the routes obtained to said
management center, and then said management center refers to said
path information to search for an existing second path having a
route overlapping the route of said second path.
64. The recording medium according to claim 63, storing said path
setting program for a management center, wherein said path setting
program is designed further comprises a second step in which when
it is determined in said first step that an already set second path
having a route overlapping the route of said second path exists,
said management center sends a message that a link can be shared in
an overlapping link group to said source node when said second path
is set.
65. The recording medium according to claim 63, storing said a path
setting program for a management center, wherein said path setting
program comprises a third step in which when it is determined in
said first step that a second path having a route overlapping the
route of said second path does not exist, said management center
sends a message that a link can not be shared to said source node
when said second path is set.
66. A recording medium storing a path setting program for a
management center in a communication network comprising a plurality
of nodes constituting a network and a management center connected
to each of said nodes, wherein each of said nodes has topology
information of said network, and said management center has
information on a risk sharing resource group and currently set path
information, and said path setting program comprises: a first step
in which a source node refers to said topology information of the
network to calculate routes of a first path and a second path and
send the routes obtained to said management center, and then said
management center refers to said information on the risk sharing
resource group to check risk sharing resource groups that the
routes of said first path and said second path sent from said
source node pass; and a second step in which when it is determined
in said first step that said risk sharing resource groups do not
overlap, said management center refers to said path information to
search for an already set second path having a route overlapping
the route of said second path.
67. The recording medium according to claim 66, storing said path
setting program for a management center, wherein said path setting
program further comprises a third step in which when an already set
second path having a route overlapping the route of said second
path exists in said second step, said risk sharing resource groups
that the route of the first path corresponding to said second path
and a route of a first path corresponding to said already set
second path pass are checked.
68. The recording medium according to claim 67, storing said path
setting program for a management center, wherein said path setting
program further comprises a fourth step in which when it is
determined in said third step that said risk sharing resource
groups of both of the first paths do not overlap, said management
center sends a message that a link can be shared in an overlapping
link group to said source node when said second path is set.
69. The recording medium according to claim 67, storing said path
setting program for a management center, wherein said path setting
program further comprises a fifth step in which when it is
determined in said third step that said risk sharing resource
groups of both of the first paths overlap, said management center
sends a message that a link can not be shared in an overlapping
link group to said source node when said second path is set.
70. A recording medium storing a path setting program for a
management center in a communication network comprising a plurality
of nodes constituting a network and a management center connected
to each of said nodes, wherein each of said nodes has topology
information of said network, and said management center has
information on a risk sharing resource group and currently set path
information, and said path setting program comprises: a first step
in which a source node refers to said topology information of the
network to calculate a route of a first path and send the route
obtained to said management center, and then said management center
refers to said information on the risk sharing resource group to
return a list of a link group not belonging to said risk sharing
resource group that the route sent from said source node passes to
said source node; and a second step in which said source node
refers to the list sent from said management center to calculate a
route of a second path and send the route obtained to said
management center, and then said management center refers to said
path information to search for an already set second path having a
route overlapping the route of said second path.
71. The recording medium according to claim 70, storing said path
setting program for a management center, wherein said path setting
program further comprises a third step in which when an already set
second path having a route overlapping the route of said second
path exists in said second step, said risk sharing resource groups
that the route of the first path corresponding to said second path
and a route of a first path corresponding to said already set
second path pass are checked.
72. The recording medium according to claim 71, storing said path
setting program for a management center, wherein said path setting
program further comprises a fourth step in which when it is
determined in said third step that said risk sharing resource
groups of both of the first paths do not overlap, said management
center sends a message that a link can be shared in an overlapping
link group to said source node when said second path is set.
73. The recording medium according to claim 71, storing said path
setting program for a management center, wherein said path setting
program further comprises a fifth step in which when it is
determined in said third step that said risk sharing resource
groups of both of the first paths overlap, said management center
sends a message that a link can not be shared in an overlapping
link group to said source node when said second path is set.
74. A recording medium storing a path setting program for a
management center in a communication network comprising a plurality
of nodes constituting a network and a management center connected
to each of the nodes, wherein each of said nodes has topology
information of said network and information on a risk sharing
resource group, and said management center has currently set path
information, and said path setting program comprises a first step
in which a source node refers to said topology information of the
network and said information on the risk sharing resource group to
calculate routes of a first path and a second path so as not to
pass the same risk sharing resource group and send the routes
obtained to said management center, and then said management center
refers to said path information to search for an already set second
path having a route overlapping the route of said second path.
75. The recording medium according to claim 74, storing said path
setting program for a management center, wherein said path setting
program further comprises a second step in which when an already
set second path having a route overlapping the route of said second
path exists in said first step, said risk sharing resource groups
that the route of the first path corresponding to said second path
and a route of a first path corresponding to said already set
second path pass are checked.
76. The recording medium according to claim 75, storing said path
setting program for a management center, wherein said path setting
program further comprises a third step in which when it is
determined in said second step that said risk sharing resource
groups of both of the first paths do not overlap, said management
center sends a message that a link can be shared in an overlapping
link group to said source node when said second path is set.
77. A recording medium storing a path setting program for a
management center in a communication network consisting of a
plurality of subnetworks, said subnetworks are networks defined in
claim 70, wherein each of said nodes comprises an external routing
table showing a boundary node that a route passes when a path to a
destination node in another subnetwork is set, and said setting
program comprises: a sixth step in which a first path and a second
path from a source node to said boundary node are set; and a
seventh step in which a first path and a second path from said
boundary node to a destination node in another subnetwork are
set.
78. The recording medium according to claim 62, storing said path
setting program for a management center, wherein said path setting
program is designed such that said first path is a primary path,
and set second path is an alternate path.
79. A path setting method according to claim 39, wherein in said
second step, signaling message to set said second path includes the
identity information of all of the risk sharing resource groups
through which said first path passes.
80. A recording medium according to claim 58, wherein in said
second step, signaling message to set said second path includes the
identity information of all of the risk sharing resource groups
through which said first path passes.
81. A nod e according to claim 21, wherein said node, next to said
calculating a first path and a second path, receives signaring
message from an upstream node including the identity informtaion of
all of the risk sharing resource groups through which said first
path passes to detect a second path having an overlapping route in
a link group betweeen the node itself and a downstream node and
compare said risk sharing resoure groups of said first path.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a communication network, a
path setting method, and a recording medium having a path setting
program recorded thereon, and more particularly to a communication
network, a path setting method, and a recording medium having a
path setting program recorded thereon in a mesh type communication
network.
[0003] 2. Description of the Related Art
[0004] Methods for forming a mesh type network in a public
communication network includes a methods using a cross connecting
unit by Synchronous Optical Network (SONET) or Synchronous Digital
Hierarchy (SDH) technique, or a method using a cross connecting
unit by Asynchronous Transfer Mode (ATM) technique, and various
failure recovery schemes are proposed in each method. A failure
recovery scheme proposed in T. Wu, "Fiber Network Service
Survivability," Artech House, 1992, Chapter 5 can be classified
into a centralized control scheme and a decentralized control
scheme. The centralized control scheme is a scheme for controlling
almost all processing steps concerning failure recovery in a
network or a subnetwork in one centralized control unit, and alarms
indicating failure detection are once centralized in the
centralized control unit, and then the centralized control unit
determines a proceeding step to be next performed based on the
alarms, and instructs several related nodes to perform the
proceeding step to detour communication traffic from a link or a
node where failure occurs. The decentralized control scheme is a
scheme in which nodes constituting a network perform failure
recovery processing in an autonomously decentralized manner.
[0005] The failure recovery scheme can be also classified into a
preplanned scheme and a dynamic scheme. In the preplanned scheme, a
route of an alternate path is previously calculated with respect to
a primary path, and occurrence of failure immediately causes switch
to the alternate path. In the dynamic scheme, a route of an
alternate path is calculated after detection of failure, and
finding the route causes switch to the alternate path. The
preplanned scheme is classified into a 1+1 and 1:1 scheme in which
one alternate path is prepared with respect to one primary path,
1:n scheme in which n (an integer not less than 2) primary paths
share one alternate path source, and m:n scheme in which n primary
paths share m (an integer not less than 2) alternate path sources.
Sharing the alternate path source achieves an advantage of
increased use efficiency of the source. However, a conflict may
occur in such a manner that the plurality of primary paths try to
take one alternate path source when multiple failures occur, so
that caution must be taken in determining which primary paths share
the alternate path source.
[0006] Attention has been recently given to technique of applying
an improved protocol that is developed for an Internet Protocol
(IP) network to an optical network to achieve high speed
provisioning and high speed failure recovery of an optical path in
the optical network. For example, in Multi-Protocol Label Switching
(MPLS) working group of Internet Engineering Task Force (IETF),
standardization of control technique of such an optical network is
implemented. In an internet draft: draft-many-ip-optical
framework-01.txt submitted to the IETF, a concept of Shared Risk
Link Group (SRLG) is introduced for facilitating route calculation
of an alternate path in failure recovery. The SRLG is a group
consisting of a plurality of links sharing the same physical
source. Sharing the same physical source means that all the links
belonging to the SRLG are affected when failure occurs in the
shared physical source. For example, a plurality of optical fibers
in the same pipe are simultaneously affected by one failure of
cutting of the pipe. In a wavelength division multiplexed optical
network, cutting of one optical fiber affects a plurality of
wavelengths in the optical fiber. The SRLG is identified by SRLG ID
and used in the route calculation of the alternate path. For
example, in page 24 of draft-many-ip-optical framework-01.txt, it
is described that a primary path and an alternate path should be
adapted not to pass links belonging to the same SRLG in 1+1 failure
recovery. In page 26 of draft-many-ip-optical framework-01.txt, it
is described that alternate paths corresponding to a plurality of
primary paths should be able to share one link simply when the
plurality of primary paths do not pass links belonging to the same
SRLG.
[0007] In this application, a group of sources sharing a risk such
as SRLG is referred to as a risk sharing resource group. Setting
paths in consideration of the risk sharing resource group can
prevent a plurality of paths from being simultaneously affected by
one failure to make failure recovery impossible.
[0008] Examples of path setting methods of this kind are described
in National Publication of International Patent Application No.
11-508421, Japanese Patent Laid-Open No. 9-224.026 and Japanese
Patent No. 2770749.
[0009] To calculate the primary path or alternate path in
consideration of the risk sharing resource group, it is necessary
to know to which risk sharing resource group the source such as the
link or node in the network belongs. Specifically, in the
decentralized control scheme, all nodes must perform route
calculation to thereby respectively have risk sharing resource
group information of the entire network. With increasing size of
the network, the amount of information becomes enormous to require
that each node has a large amount of memory source.
[0010] When a link of alternate paths corresponding to a plurality
of primary paths are to be shared, in order to determine whether a
link used in calculation of an alternate path corresponding to a
certain primary path can be shared with alternate paths
corresponding to other primary paths, it is also necessary to know
which link other all primary paths and alternate paths
corresponding thereto pass. Path information is often updated in
accordance with set or release of the path, so that there is a
problem that when all nodes have the pass information of the entire
network in the decentralized control scheme, traffic for
transmission of the pass information between the nodes
significantly increases. This problem also becomes more noticeable
with increasing size of the network.
[0011] One of means for solving the problems is, as described in
page 26 of draft-many-ip-optical framework-01.txt, to prepare a
route server having all necessary information such as topology
information of a network, information on a risk sharing resource
group, or path information, and to perform route calculation of the
primary path and alternate path by the centralized control scheme.
However, the centralized control scheme has the following problems:
1) when the size of the network is large, load of route calculation
centralized in a route server becomes too large; 2) when failure
occurs in the route server, route calculation can be no longer
performed to cause lower failure resistance than the decentralized
control scheme.
[0012] Specifically, in the conventional techniques, there are two
path setting methods:
[0013] (A) a method for imparting all information to the nodes;
and
[0014] (B) a method for imparting all information to the
centralized control unit. However, (A) has a problem that traffic
for synchronizing the information between the nodes becomes
enormous, and (B) has a problem that load of calculation is
centralized in the centralized control unit.
SUMMARY OF THE INVENTION
[0015] An object of the present invention is to provide a
communication network, a path setting method, and a recording
medium having a path setting program recorded thereon capable of
preventing load of route calculation from being centralized in part
of units, and capable of preventing traffic between nodes from
increasing.
[0016] In order to solve the above described problems, a first
aspect of the present invention provides a communication network
including: a plurality of nodes constituting a network; and a
management center connected to each of the nodes, wherein each of
the nodes has topology information of the network, and the
management center has information on a risk sharing resource
group.
[0017] A second aspect of the present invention provides a
management center connected to a plurality of nodes constituting a
network, wherein the management center has information on a risk
sharing resource group, and when each of the nodes calculates a
first path and a second path having different routes, the
management center sends the information on the risk sharing
resource group to the node.
[0018] A third aspect of the present invention provides a plurality
of nodes constituting a network, wherein each of the nodes has
topology information of the network, and when calculating a first
path and a second path having different routes, the node obtains
information on a risk sharing resource group from a management
center connected to the node.
[0019] A fourth aspect of the present invention provides a path
setting method in a communication network including a plurality of
nodes constituting a network and a management center connected to
each of the nodes, wherein each of the nodes has topology
information of the network, and the management center has
information on a risk sharing resource group, and the method
includes: a first step in which a source node refers to the
topology information of the network to calculate a route of a first
path and send the route obtained to the management center; a second
step in which the management center refers to the information on
the risk sharing resource group to return a list of a link group
not belonging to the risk sharing resource group that the route
sent from the source node passes to the source node; and a third
step in which the source node refers to the list sent from the
management center to calculate a route of a second path.
[0020] A fifth aspect of the present invention provides a recording
medium having a path setting program recorded thereon for
controlling a node in a communication network including a plurality
of nodes constituting a network and a management center connected
to each of the nodes, wherein each of the nodes has topology
information of the network, and the management center has
information on a risk sharing resource group, and the medium
includes: a first step in which a source node refers to the
topology information of the network to calculate a route of a first
path and send the route obtained to the management center; a second
step in which the management center refers to the information on
the risk sharing resource group to return a list of a link group
not belonging to the risk sharing resource group that the route
sent from the source node passes to the source node, and then the
source node refers to the list sent from the management center to
calculate a route of a second path.
[0021] A sixth aspect of the present invention provides a recording
medium having a path setting program recorded thereon for a
management center in a communication network including a plurality
of nodes constituting a network, and a management center connected
to each of the nodes, wherein each of the nodes has topology
information of the network, and the management center has
information on a risk sharing resource group, and the medium
includes a first step in which a source node refers to the topology
information of the network to calculate a route of a first path and
send the route obtained to the management center, and then the
management center refers to the information on the risk sharing
resource group to return a list of a link group not belonging to
the risk sharing resource group that the route sent from the source
node passes to the source node, and the source node refers to the
list sent from the management center to calculate a route of a
second path.
[0022] According to the first to sixth aspects of the present
invention, load of route calculation is decentralized to the nodes
and the management center to thereby prevent the load of the route
calculation from being centralized in part of units.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 shows a configuration of a network according to a
first embodiment of the invention;
[0024] FIG. 2 shows a configuration of a node 1;
[0025] FIG. 3 shows a configuration of a management center 2;
[0026] FIG. 4 shows a topology table 12;
[0027] FIG. 5 shows an SRLG table 16;
[0028] FIG. 6 shows a path table 17;
[0029] FIG. 7 shows a port table 19;
[0030] FIG. 8 shows a routing table 18;
[0031] FIG. 9 shows a topology table 12;
[0032] FIG. 10 shows a port table 19;
[0033] FIG. 11 shows a routing table 18;
[0034] FIG. 12 shows a configuration of a node 1;
[0035] FIG. 13 shows a configuration of a management center 2;
[0036] FIG. 14 shows a configuration of a network according to a
third embodiment of the invention;
[0037] FIG. 15 shows a configuration of a node 1;
[0038] FIG. 16 shows a path table 17;
[0039] FIG. 17 shows a configuration of a management center 2;
[0040] FIG. 18 shows a configuration of a network according to a
seventh embodiment of the invention;
[0041] FIG. 19 shows a configuration of a node 1;
[0042] FIG. 20 shows an external routing table 60;
[0043] FIG. 21 shows a topology table 12;
[0044] FIG. 22 shows a configuration of a network according to an
eighth embodiment of the invention;
[0045] FIG. 23 shows a configuration of a node 1;
[0046] FIG. 24 is a flowchart showing operation of the first
embodiment of the invention;
[0047] FIG. 25 is a flowchart showing operation of the first
embodiment of the invention;
[0048] FIG. 26 is a flowchart showing operation of the first
embodiment of the invention;
[0049] FIG. 27 is a flowchart showing operation of the first
embodiment of the invention;
[0050] FIG. 28 is a flowchart showing operation of a second
embodiment of the invention;
[0051] FIG. 29 is a flowchart showing operation of the third
embodiment of the invention;
[0052] FIG. 30 is a flowchart showing operation of the third
embodiment of the invention;
[0053] FIG. 31 is a flowchart showing operation of the third
embodiment of the invention;
[0054] FIG. 32 is a flowchart showing operation of a fourth
embodiment of the invention;
[0055] FIG. 33 is a flowchart showing operation of a fifth
embodiment of the invention;
[0056] FIG. 34 is a flowchart showing operation of a sixth
embodiment of the invention;
[0057] FIG. 35 is a flowchart showing operation of the sixth
embodiment of the invention;
[0058] FIG. 36 is a flowchart showing operation of the seventh
embodiment of the invention;
[0059] FIG. 37 is a flowchart showing operation of the seventh
embodiment of the invention;
[0060] FIG. 38 is a flowchart showing operation of the seventh
embodiment of the invention;
[0061] FIG. 39 shows a configuration of a node controlled by a path
setting program; and
[0062] FIG. 40 shows a configuration of a management center
controlled by a path setting program.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0063] Now, embodiments of the present invention will be described
with reference to the accompanying drawings. A first embodiment
will be described first. FIG. 1 shows a configuration of a network
of a first embodiment. With reference to the drawing, six nodes 1
(1-1 to 1-6) are linked by a two-way link group consisting of four
two-way links. In this embodiment, such a link group is provided by
preparing a 4 wavelength division multiplexing transmission line
for uplink and downlink, respectively, and a transmission format of
the link is STM-16 of SDH. A link group between the node 1-1 and
node 1-3 will be hereinafter referred to as (1, 3). This network
includes a management center 2 connected to all nodes 1.
[0064] FIG. 2 shows a configuration of the node 1. With reference
to the drawing, for a link 30 connected to an adjacent node,
Section Over Head only is terminated by a transponder 13 of SDH and
converted to a station interface 32. The node 1 is also connected
to a client (not shown in FIG. 1) by a station interface 32. These
station interfaces 32 are switched by a switch 10. A data
communication channel (D1 to D3 bytes) of the Section Over Head of
one link 30 in the link group is used as a control channel 31, and
the control channel 31 is connected to a node control unit 11. With
the control channel 31, the node control unit 11 can communicate
with a node control unit 11 of an adjacent node. The node control
unit 11 includes a topology table 12 showing a connection state of
the entire network, a routing table 18 showing connection of the
switch 10 in this node, and a port table 19 showing a connection
relationship between ports of the adjacent node and this node (FIG.
7). The node control unit 11 can communicate with the management
center 2 via a communication interface 14.
[0065] FIG. 3 shows a configuration of the management center 2.
With reference to the drawing, the management center 2 includes a
centralized control unit 15, which is connected to all nodes 1 via
the communication interface 14. The centralized control unit 15
stores an SRLG table 16 showing a relationship between the link
group and SRLG, and a path table 17 in which routes and SRLGs of a
primary path and an alternate path currently set are recorded.
[0066] Next, operation of the first embodiment will be described
with reference to the flowcharts. FIGS. 24 to 27 are flowcharts
showing the operation of the first embodiment. In the flowcharts,
at a front of a description of each step, operation of the node is
indicated by (N), and operation of the management center is
indicated by (K).
[0067] First, setting two-way primary path 20-1 and alternate path
21-1 whose source node is a node 1-1 and whose destination node is
a node 1-5 will be considered. Since they are two-way paths, there
is no source or destination in terms of flow of data, but for
convenience, a node that is a source of path setting is set as a
source node, and an opposite end is set as a destination node. Seen
from a certain node, a source side is referred to as upstream, and
a destination side is referred to as downstream.
[0068] On this network, in order for each node to understand
topology of the entire network, for example, a link state routing
protocol operates such as an extended Open Shortest Path First
(OSPF) protocol described in K. Kompella et al., "OSPF Extensions
in Support of MPL (ambda) S,"
draft-kompella-ospf-ompls-extensions-00.txt, IETF Internet Draft,
July, 2000. Therefore, the topology tables 12 of all nodes are
synchronized. The topology table 12 at this time is as shown in
FIG. 4. Here, the node 1-3 is simply indicated as 3. For example,
line 1 of FIG. 4 shows that the node 1-1 is adjacent to a node 1-2,
a metric of a link group (1, 2) connecting both nodes is 1, and the
number of currently available links is 4. The same information is
also written in line 4. That is, the node 1-2 is adjacent to the
node 1-1, the metric of the link group (1, 2) connecting both nodes
is 1, and the number of currently available links is 4. The metric
is cost of a link used for route calculation, and the number of
hops is set as the metric here.
[0069] The node control unit 11 of the node 1-1 refers to the
topology table 12 to calculate the shortest route from the node 1-1
to node 1-5 that simply passes link groups having one or more
available links, using a Constrained Shortest Path First (CSPF)
algorithm that is a calculation algorithm of the shortest route
under certain constrained conditions (S1). The CSPF algorithm is
described, for example, in B. Davie et al., "MPLS Technology and
Applications," Morgan Kaufmann Publishers, 12000, pages 175 to 180.
This calculation provides routes of link groups (1, 3), (3, 5) and
routes of link groups (1, 4), (4, 5). In this embodiment, when a
plurality of routes are obtained, a route having the smallest node
number of the hop next the source node is selected, and the routes
(1, 3), (3, 5) are selected here to be the routes of the primary
path 20-1. Then, the node 1-1 calculates the shortest route from
the node 1-1 to node 1-5 that simply passes link groups having one
or more available links except the link groups (1, 3), (3, 5), also
using the CSPF algorithm. This calculation provides the routes (1,
4), (4, 5) to be the routes of the alternate path 21-1 (different
from the routes shown in FIG. 1) (S1).
[0070] Then, the node 1-1 sends the routes of the obtained primary
path 20-1 and alternate path 21-1 to the management center 2 (S2).
The centralized control unit 15 of the management center 2 refers
to the SRLG table 16 to check SRLG that the routes of the primary
path 20-1 and alternate path 21-1 sent from the node 1-1 pass (S3).
Here, the SRLG table 16 is, for example, as shown in FIG. 5. Line 5
of this drawing shows that the link group (3, 5) belongs to two
SRLGs of SRLG 5 and SRLG 9. The SRLGs that the primary path 20-1
passes are SRLGs 2, 5, 9, and the SRLGs that the alternate path
21-1 passes are SRLGs 3, 6, 9, and it is found that SRLG 9 is an
overlap between both paths (Y in S4). That is, failures may occur
simultaneously in the primary path 20-1 and alternate path 21-1.
Thus, the management center 2 sends a rejection message with the
link group number (4, 5) of overlapping SRLG to the node
controlling unit 11 of the node 1-1 (S5).
[0071] The node 1-1 having received the rejection message
calculates the shortest route from the node 1-1 to node 1-5 that
passes link groups having one or more available links except the
link group (4, 5) as well as the link groups (1, 3), (3, 5) (S6).
This provides the routes (1, 4), (4, 6), (5, 6) to be new routes of
the alternate path 21-1.
[0072] The node 1-1 again sends the new paths of the primary path
20-1 and alternate path 21-1 to the management center 2 (S7). The
centralized control unit 15 of the management center 2 again refers
to the SRLG table 16 (S3) to find that the new alternate path 21-1
passes SRLGs 3, 7, 8. These SRLGs do not overlap the SRLGs 2, 5, 9
that the primary path 20-1 passes (N in S4, S8).
[0073] The management center 2 searches for an alternate path
having a route overlapping the route of the alternate path 21-1 in
the path table 17 (S9), but there is no such alternate path at this
time (N in S10). Thus, the management center 2 sends a permission
message to the node 1-1 (S12), and records the routes and SRLGs of
the primary path 20-1 and alternate path 21-1 in the path table 17
(S11). A state of the path table 17 at this time is shown in FIG.
6.
[0074] The node control unit 11 of the node 1-1 having received the
permission message refers to the port table 19 to set the routing
table 18 for the primary path 20-1 (S13). The port table 19 of the
node 1-1 is as shown in FIG. 7. FIG. 7 shows that a port 0 of the
node 1-1 is connected to a port 0 of the client, a port 1 to a port
1 of the client, ports 2 to 5 to ports 1 to 4 of the node 1-2,
ports 6 to 9 to ports 1 to 4 of the node 1-3, ports 10 to 13 to
ports 1 to 4 of the node 1-4, and all the ports are unused. The
node 1-1 is the source node of the primary path 20-1, and thus it
is determined that an upstream node is the client. Among unused
ports connected to the client, the port 0 having the smallest
number is selected as an upstream port. A downstream node of the
primary path 20-1 is the node 1-3, and a port 6 having the smallest
number is selected from unused ports connected to the node 1-3 as a
down stream port. Thus, the routing table 18 of the node 1-1 for
the primary path 20-1 is set as in line 1 of FIG. 8. Then, the node
1-1 signals to the node 1-3 via the control channel 31 to indicate
that the downstream port 6 allocated to the primary path 20-1 by
the node 1-1 is connected to the port 1 of the node 1-3. The node
1-3 having received it writes the upstream node of the primary path
20-1 being the node 1-1 and the upstream port being the port 1 in
the routing table 18. Next, the node 1-3 selects a downstream port
to be connected to the downstream node 1-5 in the same manner as
the node 1-1 does, and writes it in the routing table 18. The
routing table of the node 1-3 for the 20-1 is now completed.
Further, the node 1-3 signals to the node 1-5 to indicate the
number of port of the node 1-5 to which the downstream port
allocated to the primary path 20-1 is connected. The node 1-5
writes the port number in its own routing table 18 as the upstream
port. The node 1-5 is a destination and thus the downstream node is
the client, and the node 1-5 selects the downstream port connected
to the client and also writes it in the routing table 18. In this
way, the routing tables 18 of all the nodes on the primary path
20-1 are set. The nodes 1-1, 1-3, 1-5 control the switch 10 in
accordance with the routing table 18 to open the primary path 20-1
(S14). As the signaling protocol, extended Resource Reservation
Protocol (RSVP) described in D. Saha et al., "RSVP Extensions for
Signaling Optical Paths," draft-saha-rsvp-optical-signaling-00.txt,
IETF Internet Draft, 2000 may be used.
[0075] Then, the node 1-1 sets the routing table 18 for the
alternate path 21-1 as in line 2 of FIG. 8 (S15). Like the primary
path 20-1, signaling from the node 1-1 to nodes 1-4, 1-6, and 1-5
successively while selecting a downstream port in each node causes
the routing tables 18 of all the nodes on the alternate path 21-1
to be set. For the alternate path, each node 1 simply sets the
routing table 18 and reserves the port, and does not actually open
the path (S16).
[0076] Next, further setting two-way primary path 20-2 and
alternate path 21-2 whose source node is the node 1-1 and whose
destination node is the node 1-6 will be considered. At this time,
a topology table 12 of the node 1-1 is as shown in FIG. 9.
[0077] The node 1-1 refers to the topology table 12 (FIG. 9) to
calculate the shortest route from the node 1-1 to node 1-6 that
simply passes link groups having one or more available links, using
the CSPF algorithm. This calculation provides the routes (1, 2),
(2, 6), and routes (1, 4), (4, 6), but the routes (1, 2), (2, 6)
are selected in accordance with the above described rule to be the
routes of the primary path 20-2 (S1). Then, the node 1-1 calculates
the shortest route from the node 1-1 to node 1-6 that simply passes
link groups having one or more available links except the link
groups (1, 2), (2, 6), also using the CSPF algorithm. This
calculation provides the routes (1, 4), (4, 6) to be the routes of
the alternate path 21-2 (S1).
[0078] Then, the node 1-1 sends the routes of the obtained primary
path 20-2 and alternate path 21-2 to the management center 2 (S2).
The management center 2 refers to the SRLG table 16 (FIG. 5) (S3)
to find that the SRLGs that the primary path 20-2 passes are SRLGs
1, 4, and the SRLGs that the alternate path 21-2 passes are SRLGs
3, 7, and these SRLGs do not overlap (N in S4, S8).
[0079] Subsequently, the management center 2 searches for an
alternate path having a route overlapping the route of the
alternate path 21-2 in the path table 17 (FIG. 6) (S9). This time,
the primary path 20-1 and alternate path 21-1 have been recorded in
the path table 17 of the management center 2, and the route of the
alternate path 21-1 overlap the route of the alternate path 21-1 in
the link groups (1, 4), (4, 6) (Y in S10).
[0080] In descriptions in the flowcharts, the primary path and
alternate path currently set are indicated as the primary path 1
and alternate path 1, and the primary path and alternate path
already set are indicated as the primary path 2 and alternate path
2.
[0081] The management center 2 compares the SRLGs of the primary
path 20-2 and primary path 20-1 corresponding to the alternate path
21-1 (S17) to find that the SRLGs of both of them do not overlap (N
in S18).
[0082] As a result, the management center 2 sends a permission
message to the node 1-1, with the number of the alternate path 21-1
and the numbers of the overlapping link groups (1, 4), (4, 6) added
(S20). This is for setting the alternate path 21-2 so as to share
links with the alternate path 21-1 in the link groups (1, 4), (4,
6). Simultaneously, the management center 2 records the routes and
SRLGs of the primary path 20-2 and alternate path 21-2 in the path
table 17 (Sl9).
[0083] The node 1-1 having received the permission message with the
number of the alternate path 21-1 and the numbers of the link
groups (1, 4), (4, 6) first refers to the port table 19 to set the
routing table 18 for the primary path 20-2 (S21). The port table 19
at this time is as shown in FIG. 10. It is determined that an
upstream node of the primary path 20-2 is the client, an upstream
port is a port 1, a downstream port is the node 1-2, and a
downstream port is a port 2, and the node 1-1 writes them in the
routing table 18. Then, the node 1-1 signals to the node 1-2 to
indicate the port number 1 of the downstream node 1-2 connected to
the downstream port 2. The node 1-2 selects the port 1 as the
upstream port, selects the downstream port by itself, writes them
in the routing table 18, and signals to the node 1-6 that is the
downstream node to indicate the upper port number. The node 1-6 is
a destination node and thus selects the downstream port from the
ports connected to the client and writes it in the routing table.
In this way, the routing tables 18 of all the nodes on the primary
path 20-2 are set, and in accordance therewith, each node controls
the switch 10 to open the primary path 20-2.
[0084] Then, the node 1-1 sets the routing table 18 for the
alternate path 21-2 (S23). The upstream node is the client, the
upstream port is the port 1, and the downstream node is the node
1-4. When selecting the downstream port, the node 1-1 is instructed
by the management center 2 to have the alternate path 21-1 and
alternate path 21-2 share the link in the link group (1, 4) and
thus selects the port 10 identical to the downstream port of the
alternate path 21-1 as the downstream port of the alternate path
21-2. Therefore, the routing table 18 is set as shown in FIG. 11
(S23). Then, the node 1-1 signals to the node 1-4 to indicate the
upstream port number 1. Simultaneously, the node 1-1 instructs the
node 1-4 to select the same port as allocated to the alternate path
21-1, as the downstream port to be allocated to the alternate path
21-2. The extended RSVP described above has no such function, but
the RSVP can easily extend its function by adding an object. A
function of instructing a certain node to allocate the port having
allocated to a certain path to another path may be added by adding
a new object. Thereafter, similarly signaling from the node 1-4 to
node 1-6 causes the routing tables 18 of all the nodes on the
alternate path 21-2 to be set (S24).
[0085] As described above, two pairs of primary paths and alternate
paths respectively having no overlapping SRLG can be set, and two
alternate paths can be set to share a link on a certain link group,
thereby achieving effective use of source.
[0086] In the above described embodiment, the SRLGs of the primary
path 20-1 and alternate path 21-1 do not overlap, but the case
where the SRLGs overlap will be now described with reference to
FIGS. 26 and 27. When the SRLGs of the primary paths overlap (Y in
S18), the respective paths and SRLGs of the primary path 20-1 and
alternate path 21-1 are set in the path table (S25).
[0087] Then, the management center sends a permission message to
the node, but do not add information on the number of the alternate
path 21-1 or the number of overlapping link group at this time
(S26).
[0088] The node 1-1 having received the permission message first
refers to the port table 19 and sets the routing table 18 for the
primary path 20-2 (S27). Then, the node 1-1 signals to the
downstream nodes successively. Thus, the routing tables 18 of all
the nodes on the primary path 20-2 are set, and in according
therewith, each node controls the switch 10 to open the primary
path 20-2 (S28). A series of steps of opening the primary path 20-2
is the same as in the above described example.
[0089] Then, the node 1-1 sets the routing table 18 for the
alternate path 21-2 (S29). When selecting the downstream port, the
node 1-1 is not instructed by the management center 2 to have the
alternate path 21-1 and alternate path 21-2 share the link on the
overlapping link group, and thus selects a port different from the
downstream port of the alternate path 21-1 as the downstream port
of the alternate path 21-2. Then, the node 1-1 signals to the node
1-4 to indicate the upstream port number selected in such a manner
that the links do not overlap. Thereafter, similarly signaling from
the node 1-4 to node 1-6 causes the routing tables 18 of all the
nodes on the alternate path 21-2 to be set (S30).
[0090] As described above, two pairs of primary paths and alternate
paths respectively having overlapping SRLGs can be set, and two
alternate paths can be set to have no overlapping link on a certain
link group. In this way, even when the SRLGs of the primary paths
overlap and simultaneous disconnection may occur, the routes are
set in such a manner that links of the alternate paths do not
overlap, thereby preventing fatal failure.
[0091] Next, a second embodiment will be described. FIG. 1 is also
used in the second embodiment. Configurations of a node 1 and a
management center 2 in the second embodiment are shown in FIG. 12
and FIG. 13, respectively. In the second embodiment, a node control
unit 11 of the node 1 includes a topology table 12, SRLG table 16,
routing table 18, and port table 19, and a centralized control unit
15 of the management center 2 includes a path table 17. The other
configurations are identical to those in the first embodiment.
[0092] Now, operation of the second embodiment will be described
with reference to the flowchart. FIG. 28 is a flowchart showing the
operation of the second embodiment. First, setting two-way primary
path 20-1 and alternate path 21-1 whose source node is a node 1-1
and whose destination node is a node 1-5 will be considered.
[0093] The node 1-1 refers to the topology table 12 and SRLG table
16 to calculate the shortest route and the second shortest route
from the node 1-1 to node 1-5 that simply pass link groups having
one or more available links in such a manner that both routes do
not pass the same SRLG, as routes of the primary path 20-1 and the
alternate path 21-1 (S31). An algorithm calculating such a pair of
routes is described, for example, in J. Suurballe, "Disjoint Paths
in a Network," Networks, vol. 4, 1974. This calculation provides
routes (1, 3), (3, 5) as the routes of the primary path 20-1 and
routes (1, 4), (4, 6), (5, 6) as the routes of the alternate path
21-1.
[0094] The node 1-1 sends information on the routes and passing
SRLGs of the primary path 20-1 and alternate path 21-1 to the
management center 2 (S32). The management center 2 refers to the
path table 17 to search for an alternate path having a route
overlapping the route of the alternate path 21-1 (S33), but there
is no such alternate path (N in S34). Thus, the management center 2
sends a permission message to the node 1-1 (S35), and records the
routes of the primary path 20-1 and alternate path 21-1 in the path
table 17 (S36). Therefore, a state of the path table 17 is as shown
in FIG. 6.
[0095] The node 1-1 having received the permission message signals
to nodes 1-3, 1-5 (S14) as in the first embodiment, and thus the
routing tables 18 for the primary path 20-1 are set in all the
nodes 1 on the primary path 20-1 (S13). The nodes 1-1, 1-3, 1-5
control an optical switch 10 in accordance with the routing table
18 to open the primary path 20-1. Then, the node 1-1 signals to the
nodes 1-4, 1-6, 1-5 (S16), and thus the routing tables 18 for the
alternate path 21-1 are set in all the nodes 1 on the alternate
path 21-1 (S15).
[0096] Next, further setting two-way primary path 20-2 and
alternate path 21-2 whose source node is the node 1-1 and whose
destination node is the node 1-6 will be considered.
[0097] The node 1-1 refers to the topology table 12 (FIG. 9) and
the SRLG table 16 (FIG. 5) to calculate the shortest route and the
second shortest route from the node 1-1 to node 1-6 that simply
pass link groups having one or more available links in such a
manner that both routes do not pass the same SRLG, as routes of the
primary path 20-2 and the alternate path 21-2 (S31). This
calculation provides routes (1, 2), (2, 6) as the routes of the
primary path 20-2 and routes (1, 4), (4, 6) as the routes of the
alternate path 21-2.
[0098] Then, the node 1-1 sends the routes obtained of the primary
path 20-2 and alternate path 21-2 to the management center 2 (S32).
The management center 2 refers to the path table 17 (FIG. 6) to
search for an alternate path having a route overlapping the route
of the alternate path 21-2 (S33). This time, the primary path 20-1
and alternate path 21-1 have been recorded in the path table 17,
and the routes of the alternate path 21-1 overlaps the routes of
the alternate path 21-2 in the link groups (1, 4), (4, 6) (Y in
S34). The management center 2 compares the SRLGs of the primary
path 20-2 and primary path 20-1 corresponding to the alternate path
21-1 (S17) to find that the SRLGs of both of them do not overlap (N
in S18).
[0099] As a result, the management center 2 sends a permission
message to the node 1-1, with the number of the alternate path 21-1
and the numbers of the overlapping link groups (1, 4), (4, 6) added
(S20). Simultaneously, the management center 2 records the routes
and SRLGs of the primary path 20-2 and alternate path 21-2 in the
path table 17 (S19).
[0100] Thereafter, in accordance with completely the same steps as
in the first embodiment, the primary path 20-2 and alternate path
21-2 are set, and the alternate paths 21-1 and 21-2 share links on
the link groups (1, 4), (4, 6).
[0101] As described above, two pairs of primary paths and alternate
paths respectively having no overlapping SRLG can be set, and two
alternate paths can be set to share a link on a certain link group.
Processing when the SRLGs of the primary path 1 and primary path 2
overlap is the same as in the first embodiment.
[0102] Next, a third embodiment will be described. FIG. 14 shows a
configuration of a network of the third embodiment. In the third
embodiment, there is no centralized management center. FIG. 15
shows a configuration of a node 1. The node 1 in this embodiment
additionally has a path table 17. However, the path table 17 simply
records information on a primary path passing the node 1 itself and
an alternate path corresponding thereto, or an alternate path
passing the node 1 itself and a primary path corresponding thereto.
There is no communication interface for communication with the
centralized management center. The other configurations are
identical to those in the second embodiment.
[0103] Now, operation of the third embodiment will be described
with reference to the flowchart. FIGS. 29 to 31 are flowcharts
showing the operation of the third embodiment. First, setting
two-way primary path 20-1 and alternate path 21-1 whose source node
is a node 1-1 and whose destination node is a node 1-5 will be
considered.
[0104] The node 1-1 calculates routes of the primary path 20-1 and
alternate path 21-1 in the same manner as in the second embodiment,
and obtains routes (1, 3), (3, 5) as the routes of the primary path
20-1 and routes (1, 4), (4, 6), (5, 6) as the routes of the
alternate path 21-1 (S51). The node 1-1 records information on the
routes and SRLGs of the primary path 20-1 and alternate path 21-1
in the path table 17 as shown in FIG. 6 (S52).
[0105] Next, the node 1-1 sets the routing table 18 for the primary
path 20-1 (S53). The setting manner is the same as in the first
embodiment. That is, the routing table 18 is set as in line 1 of
FIG. 11.
[0106] Then, the node 1-1 signals to a downstream node 1-3 to
indicate an upstream port number 1 (S54). The node 1-3 writes the
number in its own routing table 18. This signaling also indicates
the information on the routes and SRLGs of the primary path 20-1
and alternate path 21-1, and the node 1-3 records the information
in its own path table 17. However, it is sufficient for the
information to include that of a route of the althernate path 21-1
and SRLGs of the primary path 20-1, at least.
[0107] Next, the node 1-3 sets the routing table 18 for the primary
path 20-1. The setting manner is the same as in the first
embodiment.
[0108] Then, the node 1-3 signals to the downstream node 1-5 to
indicate an upstream port number. The node 1-5 writes the number in
its own routing table 18. This signaling also indicates the
information on the routes and SRLGs of the primary path 20-1 and
alternate path 21-1, and the node 1-5 records the information in
its own path table 17.
[0109] Next, the node 1-5 sets the routing table 18 for the primary
path 20-1. The setting manner is the same as in the first
embodiment.
[0110] In this way, setting of the routing tables 18 for the
primary path 20-1 in the nodes on the primary path 20-1 is
completed, and each node controls a switch 10 in accordance
therewith to open the primary path 20-1.
[0111] Next, the node 1-1 sets the routing table 18 for the
alternate path 21-1 (S55). The node 1-1 refers to the path table 17
and searches for another alternate path passing the link group (1,
4) like the alternate path 21-1 (S56), but there is no such
alternate path (N in S57). Thus, the node 1-1 allocates an unused
port to a downstream port of the alternate path 21-1 (S58). That
is, the routing table 18 is set as in line 2 of FIG. 11.
[0112] Then, the node 1-1 signals to a downstream node 1-4 of the
alternate path 21-1 to indicate an upstream port number 1 (S59).
The node 1-4 writes the number in its own routing table 18 (N in
S60, S61). This signaling also indicates the information on the
routes and SRLGs of the primary path 20-1 and alternate path
21-1.
[0113] The node 1-4 refers to its own path table 17 and searches
for another alternate path passing the link group (4, 6) like the
alternate path 21-1 (S56), but there is no such alternate path (N
in S57). Thus, the node 1-4 allocates an unused port to a
downstream port of the alternate path 21-1 (S58). The node 1-4
records the information on the routes and SRLGs of the primary path
20-1 and alternate path 21-1 in the path table 17.
[0114] Then, the node 1-4 signals to a downstream node 1-6 of the
alternate path 21-1 to indicate an upstream port number (S59). The
node 1-6 writes the number in its own routing table 18 (N in S60,
S61). This signaling also indicates the information on the routes
and SRLGs of the primary path 20-1 and alternate path 21-1.
[0115] The node 1-6 refers to its own path table 17 and searches
for another alternate path passing the link group (5, 6) like the
alternate path 21-1 (S56), but there is no such alternate path (N
in S57). Thus, the node 1-6 allocates an unused port to a
downstream port of the alternate path 21-1 (S58). The node 1-6
records the information on the routes and SRLGs of the primary path
20-1 and alternate path 21-1 in the path table 17.
[0116] Next, the node 1-6 signals to a downstream node 1-5 of the
alternate path 21-1 to indicate an upstream port number (S59). The
node 1-5 writes the number in its own routing table 18 (S60) This
signaling also indicates the information on the routes and SRLGs of
the primary path 20-1 and alternate path 21-1.
[0117] The node 1-5 is a destination node of the alternate path
21-1 (Y in S61), and thus allocates the same port as allocated to
the primary path 20-1, that is, the port connected to the client,
to the downstream port of the alternate path 21-1 (S62). The node
1-5 also records the information on the routes and SRLGs of the
primary path 20-1 and alternate path 21-1 in the path table 17.
[0118] In this way, setting of the routing tables 18 for the
alternate path 21-1 in the nodes on the alternate path 21-1 is
completed (S63).
[0119] Next, further setting two-way primary path 20-2 and
alternate path 21-2 whose source node is the node 1-1 and whose
destination node is the node 1-6 will be considered.
[0120] The node 1-1 calculates routes of the primary path 20-2 and
alternate path 21-2 in the same manner as in the second embodiment,
and obtains routes (1, 2), (2, 6) as the routes of the primary path
20-2 and routes (1, 4), (4, 6) as the routes of the alternate path
21-1 (S51). The node 1-1 records information on the routes and
SRLGs of the primary path 20-2 and alternate path 21-2 in the path
table 17 as shown in FIG. 16 (S52).
[0121] Next, the node 1-1 sets the routing table 18 for the primary
path 20-2 (S53). The setting manner is the same as in the first
embodiment. That is, the routing table 18 is set as in line 3 of
FIG. 11.
[0122] Then, the node 1-1 signals to a downstream node 1-2 of the
primary path 20-2 to indicate an upstream port number 1 (S54). The
node 1-2 writes the number in its own routing table 18. This
signaling also indicates the information on the routes and SRLGs of
the primary path 20-2 and alternate path 21-2, and the node 1-2
records the information in its own path table 17.
[0123] Next, the node 1-2 sets the routing table 18 for the primary
path 20-2 (S53). The setting manner is the same as in the first
embodiment.
[0124] Then, the node 1-2 signals to the downstream node 1-6 to
indicate an upstream port number. The node 1-6 writes the number in
its own routing table 18. This signaling also indicates the
information on the routes and SRLGs of the primary path 20-2 and
alternate path 21-2, and the node 1-6 records the information in
its own path table 17.
[0125] Next, the node 1-6 sets the routing table 18 for the primary
path 20-2. The setting manner is the same as in the first
embodiment.
[0126] In this way, setting of the routing tables 18 for the
primary path 20-2 in the nodes on the primary path 20-2 is
completed, and each node controls a switch 10 in accordance
therewith to open the primary path 20-2.
[0127] Next, the node 1-1 sets the routing table 18 for the
alternate path 21-2 (S55). The node 1-1 refers to the path table 17
(FIG. 16) and searches for another alternate path passing the link
group (1, 4) like the alternate path 21-2 (S56). The alternate path
21-1 applies thereto here (Y in S57). The node 1-1 compares the
SRLGs of the primary path 20-1 and primary path 20-2 that are
recorded in the path table 17 (S68) to find that the SRLGs of both
of them do not overlap (N in S69). Thus, the node 1-1 allocates the
same port 10 as allocated to the alternate path 21-1, as the
downstream port of the alternate path 21-2 (S70). Therefore, the
routing table of the node 1-1 is as shown in FIG. 11.
[0128] Then, the node 1-1 signals to the downstream node 1-4 of the
alternate path 21-2 to indicate an upstream port number 1 (S71).
The node 1-4 writes the number in its own routing table 18 (Nin
S72, S73). This signaling also indicates the information on the
routes and SRLGs of the primary path 20-2 and alternate path 21-2,
and the node 1-4 records the information in its own path table
17.
[0129] The node 1-4 refers to the path table 17 and searches for
another alternate path passing a link group (4, 6) like the
alternate path 21-2 (S56). The alternate path 21-1 applies thereto
here (Y in S57). Thus, the node 1-4 compares the SRLGs of the
primary path 20-1 and primary path 20-2 that are recorded in the
path table 17 (S68) to find that the SRLGs of both of them do not
overlap (N in S69). Therefore, the node 1-4 allocates the same port
as allocated to the alternate path 21-1, as the downstream port of
the alternate path 21-2 (S70).
[0130] Next, the node 1-4 signals to the downstream node 1-6 of the
alternate path 21-2 to indicate an upstream port number (S71). The
node 1-6 writes the number in its own routing table 18 (S72). This
signaling indicates the information on the routes and SRLGs of the
primary path 20-2 and alternate path 21-2.
[0131] The node 1-6 is a destination node of the alternate path
21-2 (Y in S73), and thus allocates the same port as allocated to
the primary path 20-2, that is, the port connected to the client,
to the downstream port of the alternate path 21-2 (S74). The node
1-6 also records the information on the routes and SRLGs of the
primary path 20-2 and alternate path 21-2 in the path table 17. In
this way, setting of the routing tables 18 for the alternate path
21-2 in the nodes on the alternate path 21-2 is completed (S75).
The alternate paths 21-1 and 21-2 share links on the link groups
(1, 4), (4, 6).
[0132] When the SRLGs of the primary path 20-1 and primary path
20-2 overlaps at step 69 (Y in S69), the node 1-4 allocates a port
different from that allocated to the alternate path 21-1, as the
downstream port of the alternate path 21-2 (S76).
[0133] As described above, two pairs of primary paths and alternate
paths respectively having no overlapping SRLG can be set, and two
alternate paths can be set to share a link on a certain link
group.
[0134] Next, a fourth embodiment will be described. In the fourth
embodiment, configurations of a network, nodes, and a management
center are the same as in the first embodiment, and calculation
steps only of routes of a primary path and an alternate path are
different.
[0135] Now, operation of the fourth embodiment will be described
with reference to the flowchart. FIG. 32 is a flowchart showing the
operation of the fourth embodiment. A node control unit 11 of a
node 1-1 first calculates a route of a primary path 20-1 in the
same manner as in the first embodiment (S81). Then, the node 1-1
sends the route obtained of the primary path 20-1 to a management
center 2 (S82). A centralized control unit 15 of the management
center 2 records the route in a path table 17. Next, the
centralized control unit 15 refers to a SRLG table 16 to prepare a
list of a link group not belonging to SRLG that the route of the
primary path 20-1 sent from the node 1-1 passes, and returns the
list to the node 1-1 (S83). Here, a list of link groups (1, 2), (1,
4), (2, 6), (4, 6), (5, 6) is sent. The node 1-1 calculates the
shortest route from the node 1-1 to node 1-5 simply using link
groups having one or more available links among link groups
included in the list (S84). This provides the routes (1, 4), (4,
6), (5, 6) to be the routes of the alternate path 21-1.
[0136] The node 1-1 sends the routes of the alternate path 21-1 to
the management center 2 (S85). The management center 2 searches for
an alternate path having a route overlapping the route of the
alternate path 21-1 in the path table 17 (S86), but there is no
such alternate path at this time (N in S87). Thus, the management
center 2 sends a message indicating "share no resource" to the node
1-1 (S88), and records the routes of the alternate path 21-1 in the
path table 17. A state of the path table 17 at this time is as
shown in FIG. 6.
[0137] Subsequently, the node 1-1 signals to the nodes on the
primary path 20-1 and alternate path 21-1 as in the first
embodiment, and sets the primary path 20-1 and alternate path 21-1
(S89).
[0138] Next, further setting two-way primary path 20-2 and
alternate path 21-2 whose source node is the node 1-1 and whose
destination node is the node 1-6 in this network will be
considered.
[0139] The node 1-1 calculates a route of a primary path 20-2 also
in the same manner as in the first embodiment (S81). The node 1-1
sends the route to the management center 2 (S82). The centralized
control unit 15 of the management center 2 records the route in the
path table 17. Next, the centralized control unit 15 refers to the
SRLG table 16 to prepare a list of a link group not belonging to
SRLG that the route of the primary path 20-2 sent from the node 1-1
passes, and returns the list to the node 1-1 (S83). Here, a list of
link groups (1, 3), (1, 4), (3, 5), (4, 5), (4, 6), (5, 6) is sent.
The node 1-1 calculates the shortest route from the node 1-1 to
node 1-5 simply using link groups having one or more available
links among link groups included in the list (S84). This provides
the routes (1, 4), (4, 6) to be the routes of the alternate path
21-2.
[0140] The node 1-1 sends the routes of the alternate path 21-2 to
the management center 2 (S85), and the centralized control unit 15
of the management center 2 records the routes in the path table
17.
[0141] Then, the management center 2 searches for an alternate path
having a route overlapping the route of the alternate path 21-2 in
the path table 17 (S86), and determines whether a resource of the
alternate path can be shared based on SRLG of a corresponding
primary path (S87). Operation thereafter is completely the same as
in the first embodiment. As described above, two pairs of primary
paths and alternate paths respectively having no overlapping SRLG
can be set, and two alternate paths can be set to share a link on a
certain link group.
[0142] Next, a fifth embodiment will be described. In the fifth
embodiment, configurations of a network and nodes are the same as
in the first embodiment, and a configuration of a management center
is different. The fifth embodiment is also similar to the fourth
embodiment in that calculation results of routes of a primary path
are sent to the management center before routes of an alternate
path are calculated.
[0143] The management center 2 in this embodiment includes an SRLG
table 16 as shown in FIG. 17, but includes no path table 17. In
this embodiment, setting manner of a primary path 20-1 and
alternate path 21-1 will be described.
[0144] Now, operation of the fifth embodiment will be described
with reference to the flowchart. FIG. 33 is a flowchart showing the
operation of the fifth embodiment. A node control unit 11 of a node
1-1 first calculates a route of a primary path 20-1 in the same
manner as in the fourth embodiment (S81 in FIG. 32). Then, the node
1-1 sends the route obtained of the primary path 20-1 to a
management center 2 (S82). A centralized control unit 15 of the
management center 2 refers to a SRLG table 16 to prepare a list of
a link group not belonging to SRLG that the route of the primary
path 20-1 sent from the node 1-1 passes, and returns the list to
the node 1-1 (S83). Here, a list of link groups (1, 2), (1, 4), (2,
6), (4, 6), (5, 6) is sent. The node 1-1 calculates the shortest
route from the node 1-1 to node 1-5 simply using link groups having
one or more available links among link groups included in the list
(S84). This provides the routes (1, 4), (4, 6), (5, 6) to be the
route of the alternate path 21-1.
[0145] Subsequently, the node 1-1 signals to the nodes on the
primary path 20-1 and alternate path 21-1 as in the first
embodiment, and sets the primary path 20-1 and alternate path 21-1
(S91 in FIG. 33).
[0146] In this way, a pair of primary path and alternate path
having no overlapping SRLG can be set.
[0147] Next, a sixth embodiment will be described. In the sixth
embodiment, configurations of a network and nodes are the same as
in the first embodiment, and a configuration of a management center
is different. A management center 2 in this embodiment includes a
path table 17 as shown in FIG. 13, but includes no SRLG table
16.
[0148] Now, operation of the sixth embodiment will be described
with reference to the flowcharts. FIGS. 34 and 35 are flowcharts
showing the operation of the sixth embodiment. A node control unit
11 of a node 1-1 first calculates a route of a primary path 20-1 in
the same manner as in the first embodiment. This provides the
routes (1, 3), (3, 5) of the primary path 20-1.
[0149] The node 1-1 calculates the shortest route from the node 1-1
to node 1-5 that simply passes link groups having one or more
available links except the link groups (1, 3), (3, 5). This
calculation provides the routes (1, 4), (4, 5) to be the routes of
the alternate path 21-1 (S101).
[0150] Then, the node 1-1 sends the routes of the obtained primary
path 20-1 and alternate path 21-1 to the management center 2
(S102). The management center 2 searches for an alternate path
having a route overlapping the route of the alternate path 21-1 in
the path table 17 (S103), but there is no such alternate path at
this time (N in S104). Thus, the management center 2 sends a
message indicating "have no link shared in setting the alternate
path 21-2" to the node 1-1 (S105), and records the routes of the
primary path 20-1 and alternate path 21-1 in the path table 17.
[0151] Subsequently, the node 1-1 signals to the nodes on the
primary path 20-1 and alternate path 21-1 as in the first
embodiment, and sets the primary path 20-1 and alternate path 21-1
(S106).
[0152] Next, further setting two-way primary path 20-2 and
alternate path 21-2 whose source node is the node 1-1 and whose
destination node is the node 1-6 in this network will be
considered.
[0153] The node 1-1 calculates a route of a primary path 20-2 also
in the same manner as in the first embodiment (S81). This provides
the routes (1, 2), (2, 6) of the primary path 20-2.
[0154] Then, the node 1-1 calculates the shortest route from the
node 1-1 to node 1-6 that simply passes link groups having one or
more available links except the link groups (1, 2), (2, 6). This
calculation provides the routes (1, 4), (4, 6) to be the routes of
the alternate path 21-2 (S101).
[0155] Next, the node 1-1 sends the routes of the obtained primary
path 20-2 and alternate path 21-2 to the management center 2
(S102). The management center 2 searches for an alternate path
having a route overlapping the route of the alternate path 21-2 in
the path table 17 (S103). The alternate path 21-1 overlaps the
alternate path 21-2 in the link group (1, 4) (Y in S104). Thus, the
management center 2 sends a message indicating "have the link
shared with the alternate paths 21-1 in the link group (1, 4) in
setting the alternate path 21-2" to the node 1-1 (S107), and
records the route of the primary path 20-2 and alternate path 21-2
in the path table 17.
[0156] Subsequently, the node 1-1 signals to the nodes on the
primary path 20-2 and alternate path 21-2 as in the first
embodiment, and sets the primary path 20-2 and alternate path 21-2
(S108).
[0157] As described above, two pairs of primary paths and alternate
paths respectively sharing no link can be set, and two alternate
paths can be set to share a link on a certain link group.
[0158] Next, a seventh embodiment will be described. A
configuration of a network of the seventh embodiment is shown in
FIG. 18. In this embodiment, the network consists of three
subnetworks 3-a, 3-b, 3-c. A configuration of each subnetwork is
the same as that of the network in the first embodiment. A node 1-5
of the subnetwork 3-a and a node 1-2b of the subnetwork 3-b are
connected by a primary link group 40-ab and an alternate link group
41-ab respectively consisting of four links. Using the two link
groups, failure recovery by an Automatic Protection Switching (APS)
scheme is performed between the nodes 1-5a and 1-2b. The APS scheme
is described in T. Wu, "Fiber Network Service Survivability,"
Artech House, 1992, Chapter 3 and soon. Likewise, failure recovery
by the APS scheme using a primary link group 40-ac and alternate
link group 41-ac is performed between the subnetworks 3-a and
3-c.
[0159] A configuration of a node 1 in this embodiment is shown in
FIG. 19. The configuration is the same as that of the node 1 in the
first embodiment except for presence of an external routing table
60 in a node control unit 11. A topology table 12 of the node 1 in
the subnetwork 3-a holds topology information in the subnetwork
3-a, that is, the contents of FIGS. 4 and 21. The external routing
table 60 shows a node that a route passes when a path to a
destination node in another subnetwork is set, that is, a boundary
node. An example of the external routing table 60 is shown in FIG.
20. FIG. 20 shows that the node 1-5a is a boundary node when a path
whose destination is the subnetwork 3-b is set, and that the node
1-6a is a boundary node when a path whose destination is the
subnetwork 3-c. A configuration of a management center 2 of this
embodiment is the same as that of the management center 2 in the
first embodiment. An SRLG table 16 in the management center 2 of
the subnetwork 3-a holds SRLG information in the subnetwork 3-a,
that is, the same contents as FIG. 5. In a path table 17, routes
and SRLGs of the paths in the subnetwork 3-a are recorded.
[0160] Now, operation of the seventh embodiment will be described
with reference to the flowcharts. FIGS. 36 and 37 are flowcharts
showing the operation of the seventh embodiment.
[0161] Setting a primary path 20-1 and alternate path 21-1 whose
source is the node 1-1a in the subnetwork 3-a and whose destination
is the node 1-5b in the subnetwork 3-b will be considered.
[0162] A node control unit 11 of the node 1-1a first refers to the
external routing table 60 to find that the route may pass the node
1-5a when the path whose destination is the node in the subnetwork
3-b (S111) is set. The node control unit 11 of the node 1-1a refers
to the topology table 12 to calculate the shortest route from the
node 1-1a to node 1-5a that simply passes link groups having one or
more available links, using the CSPF algorithm. This provides the
routes (1, 3), (3, 5) of the primary path 20-1 (S81 in FIG.
32).
[0163] Then, the node 1-1a sends the routes obtained (1, 3), (3, 5)
of the primary path 20-1 to the management center 2-a (S82). A
centralized control unit 15 of the management center 2-a records
the routes in the path table 17. Next, the centralized control unit
15 refers to the SRLG table 16 to prepare a list of a link group
not belonging to SRLG that the routes of the primary path 20-1 sent
from the node 1-1a pass, and returns the list to the node 1-1a
(S83). Here, a list of link groups (1, 2), (1, 4), (2, 6), (4, 6),
(5, 6) is sent. The node 1-1a calculates the shortest route from
the node 1-1a to node 1-5a simply using link groups having one or
more available links among link groups included in the list (S84).
This provides the routes (1, 4), (4, 6), (5, 6) to be the routes of
the alternate path 21-1.
[0164] The node 1-1a also sends the routes of the alternate path
21-1 to the management center 2-a (S85). The management center 2-a
searches for an alternate path having a route overlapping the route
of the alternate path 21-1 in the path table 17 (S86), but there is
no such alternate path at this time (N in S87). Thus, the
management center 2-a sends a message indicating "share no
resource" to the node 1-1a (S88), and records the routes of the
alternate path 21-1 in the path table 17. A state of the path table
17 at this time is shown in FIG. 6.
[0165] Then, the node 1-1a refers to a port table 19 to set the
routing table 18 for the primary path 20-1 (S113 in FIG. 36). The
node 1-1a is the source node of the primary path 20-1, and thus an
upstream node is a client. Among ports connected to the client, the
port 0 having the smallest number is selected as an upstream port.
A downstream node of the primary path 20-1 is the node 1-3a, and a
port 6 having the smallest number is selected from unused ports
connected to the node 1-3 as a downstream port. Thus, the routing
table 18 of the node 1-1a for the primary path 20-1 is set as in
line 1 of FIG. 8.
[0166] Then, the node 1-1a sends a setting request message of the
primary path 20-1 that is a kind of signaling messages to the node
1-3a via a control channel 31. The setting request message includes
information such as identification data of the message,
identification data indicating that this path is the primary path,
path number, source node number, destination node number, route
information to the node 1-5a, and upstream port number of the
downstream node. The upstream port number of the downstream node is
a port of the node 1-3a connected to a downstream port 6 allocated
to the primary path 20-1 by the node 1-1a, that is, a port 1.
[0167] The node 1-3a having received the setting request message
writes the upstream node of the primary path 20-1 being the node
1-1a and the upstream port being the port 1 in the routing table
18. Next, the node 1-3a selects a downstream port to be connected
to the downstream node 1-5a in the same manner as the node 1-1a
does, and writes it in the routing table 18. The routing table of
the node 1-3a for the 20-1 is now completed. Further, the node 1-3a
rewrites the upstream port number of the downstream node in the
setting request message, and sends the setting request message to
the node 1-5a.
[0168] The node 1-5a can find the upstream node (node 1-3a) and the
upstream port number for the primary path 20-1 by the setting
request message, and thus writes them in its own routing table 18.
The node 1-5a has known that the node 1-5a itself is the boundary
node for the path to the subnetwork 3-b. In the setting request
message of the primary path 20-1 received by the node 1-5a, it is
also written that the destination of the path is the node 1-5b in
the subnetwork 3-b, so that the node 1-5a writes the node 1-2b in
the routing table 18 as a downstream node number for the primary
path 20-1, and selects the port having the smallest port number
from the ports connected to the link included in the link group
40-ab as the downstream port, and also writes it in the routing
table 18. Then, the node 1-5a rewrites the upstream port number of
the downstream node in the setting request message into the port
number of the node 1-2b connected to the downstream port selected
by the node 1-5a itself, and sends the setting request message to
the node 1-2b (S114).
[0169] Next, the node 1-1a sets the routing table 18 for the
alternate path 21-1 as in line 2 of FIG. 8 (S115). The node 1-1a is
the source of the alternate path 21-1, so that the upstream node
and upstream port are identical to those of the primary path 20-1,
the downstream node is a node 1-4a, and a port 10 having the
smallest port number is selected from the ports connected to the
node 1-4a as the downstream port.
[0170] Subsequently, the node 1-1a generates a setting request
message of the alternate path 21-1 and sends it to the node 1-4a
via the control channel 31. The setting request message includes
information such as identification data of the message,
identification data indicating that this path is the alternate
path, path number, source node number, destination node number,
route information to the node 1-5a, upstream port number of the
downstream port, and identification data indicating that this path
shares no resource with another alternate path. The upstream port
number of the downstream node is set to 10 that is the port number
of the node 1-4a connected to the port 10 of the node itself.
[0171] The node 1-4a having received this message writes the
upstream port number 10 for the alternate path 21-1 in the routing
table 18, selects the downstream port and write it in the routing
table 18, and then rewrites the upstream port number of the
downstream node in the setting request message and send it to a
node 1-6a.
[0172] The node 1-6a similarly sets the routing table, and then
transfers the setting request message to the node 1-5a.
[0173] The node 1-5a having received the setting request message of
the alternate path 21-1 first writes the received upstream port
number in the routing table 18. The node 1-5a selects the
downstream node number and downstream port number as in the primary
path 20-1, and writes them in the routing table 18. Then, the node
1-5a rewrites the upstream port number of the downstream node of
the setting request message and sends it to the node 1-2b that is
the downstream node (S116).
[0174] In this way, setting of the routing table 18 for the primary
path 20-1 and alternate path 21-1 in the subnetwork 3-a is
completed (S117).
[0175] On the other hand, the topology table 12 in the subnetwork
3-b stores topology information in the subnetwork 3-b, the contents
of FIG. 4, and information that the node 1-2b is connected to the
node 1-5a of the subnetwork 3-a. The SRLG table 16 in the
management center 2 of the subnetwork 3-b holds SRLG information in
the subnetwork 3-b, that is, the same contents as FIG. 5. In the
path table 17, routes and SRLGs of the path in the subnetwork 3-b
are recorded.
[0176] In the subnetwork 3-b, the node 1-2b first receives the
setting request message of the primary path 20-1 from the node 1-5a
(S12) (S121 in FIG. 37). This message indicates that the
destination node of this path is the node 1-5b in the same
subnetwork, but does not indicate the route thereto. Thus, the node
1-2b refers to its own topology table 12 to calculate the shortest
route from the node 1-2b to node 1-5b that simply passes link
groups having one or more available links, using the CSPF algorithm
(S81 in FIG. 32). This provides the routes (2, 6), (5, 6) to be the
routes of the primary path 20-1. Then, the node 1-2b sends the
routes obtained to a management center 2-b (S82). A centralized
control unit 15 of the management center 2-b records the routes in
the path table 17. Next, the centralized control unit 15 refers to
the SRLG table 16 to prepare a list of a link group not belonging
to SRLG that the routes of the primary path 20-1 sent from the node
1-2b pass, and returns the list to the node 1-2b (S83). Here, a
list of link groups (1, 2), (1, 3), (1, 4), (3, 5), (4, 5), (4, 6)
is sent. Then, the node 1-2b calculates the shortest route from the
node 1-2b to node 1-5b simply using link groups having one or more
available links among link groups included in the list (S84). This
provides the routes (1, 2), (1, 3), (3, 5) to be the routes of the
alternate path 21-1.
[0177] The node 1-2b also sends the routes of the alternate path
21-1 to the management center 2-b (S85). The management center 2-b
searches for an alternate path having a route overlapping the route
of the alternate path 21-1 in the path table 17, but there is no
such alternate path at this time (N in S87). Thus, the management
center 2-b sends a message indicating "share no resource" to the
node 1-2b (S88), and records the routes of the alternate path 21-1
in the path table 17.
[0178] Subsequently, the node 1-2b sets the routing table 18 for
the primary path 20-1 (S123 in FIG. 37), and then writes the route
from the node 1-2b to the node 1-5b in the setting request message,
and send it to the node 1-6b that is the downstream node. The node
1-6b also sets the routing table 18, and then rewrites the setting
request message and sent it to the node 1-5b. In these nodes,
setting of the routing table 18 and signaling of the setting
request message are performed in completely the same manner as
performed for the primary path 20-1 in the subnetwork 3-a.
[0179] Finally, the node 1-5b having received the setting request
message sets the upstream port of the routing table 18 as specified
by the node 1-6b (S124). The node 1-5b is the destination node of
the primary path 20-1, so that the downstream node is the client,
and the port having the smallest port number is selected from the
ports connected to the client as the downstream port. The node 1-5b
also writes this information in the routing table 18. The node 1-5b
changes a switch 10 in accordance with the contents of the routing
table 18, and then generates a setting response message that is a
kind of signaling messages and sends it to the node 1-6b. The
setting response message includes information such as
identification data of the message, identification data indicating
that this path is the primary path, path number, source node
number, and destination node number. The setting response message
is transferred in a direction opposite the path on the route of the
primary path 20-1 to the node 1-1a that is the source node (S125).
Each node on the route receives the setting response message to
change its own switch 10 in accordance with the contents of the
routing table 18. In this way, setting of the primary path 20-1 is
completed (S126).
[0180] Then, the node 1-2b sets the routing table 18 for the
alternate path 21-1 (S127), writes the route information of the
alternate path 21-1 in the subnetwork 3-b in the setting request
message, and sends it to the node 1-1b. The setting request message
is transferred from the node 1-1b to the node 1-3b and node 1-5b,
and the routing table 18 is set in each node on the way (S128). The
source is not shared with another alternate path, and setting of
the routing table 18 and signaling of the setting request message
are performed in completely the same manner as performed for the
alternate path 21-1 in the subnetwork 3-a.
[0181] In the node 1-5b, the same port as allocated to the primary
path 20-1 is allocated as the downstream port for the alternate
path 21-1. When setting of the routing table 18 is completed, the
node 1-5b generates the setting response message. This message is
transferred in a direction opposite the path on the route of the
alternate path 21-1 to the node 1-1a that is the source node
(S129). Each node on the route does not change the switch 10 when
it receives the setting response message to the alternate path. In
this way, setting of the alternate path 21-1 is completed
(S130).
[0182] Next, setting a primary path 20-2 and alternate path 21-2
whose source is the node 1-1a in the subnetwork 3-a and whose
destination is a node 1-6c in a subnetwork 3-c will be
considered.
[0183] The node control unit 11 in the node 1-1a first refers to
the external routing table 60 to find that the route may pass the
node 1-6a when the path whose destination is the node in the
subnetwork 3-c (S111 in FIG. 36) is set. The node control unit 11
of the node 1-1a calculates the shortest route from the node 1-1a
to node 1-6a that simply passes link groups having one or more
available links (S81 in FIG. 32). This provides the routes (1, 2),
(2, 6) of the primary path 20-2.
[0184] Then, the node 1-1a sends the routes obtained of primary
path 20-1 to the management center 2-a (S82). The centralized
control unit 15 of the management center 2-a records the routes in
the path table 17. Next, the centralized control unit 15 refers to
the SRLG table 16 to prepare a list of a link group not belonging
to SRLG that the routes of the primary path 20-2 sent from the node
1-1a pass, and returns the list to the node 1-1a (S83). Here, a
list of link groups (1, 3), (1, 4), (3, 5), (4, 5), (4, 6), (5, 6)
is sent. The node 1-1a calculates the shortest route from the node
1-1a to node 1-6a simply using link groups having one or more
available links among link groups included in the list (S84). This
provides the routes (1, 4), (4, 6) to be paths of the alternate
path 21-2.
[0185] The node 1-1a also sends the routes of the alternate path
21-2 to the management center 2-a (S85). The centralized control
unit 15 of the management center 2 searches for an alternate path
having a route overlapping the route of the alternate path 21-2 in
the path table 17 (S86). The alternate path 21-1 overlaps the
alternate path 21-2 in the link groups (1, 4), (4, 6) (Y in S87)
here. Thus, the centralized control unit 15 checks the SRLGs that
the routes of the primary path 20-1 and primary path 20-2
corresponding to the alternate paths pass (S17 in FIG. 26). The
SRLGs of both primary paths do not overlap (N in S18), so that the
centralized control unit 15 sends a message indicating "share the
link with the alternate path 21-1 in the link groups (1, 4), (4,
6)" to the node 1-1a, and records the routes of the alternate path
21-2 in the path table 17 (Sl9).
[0186] Subsequently, the node 1-1a sets the routing table 18 for
the primary path 20-2 (S20, S21), and then generates the setting
request message. The setting request message is transferred to the
node 1-6a via the node 1-4a (S22). In accordance therewith, the
routing tables for the 20-2 are also set in the node 1-4a and node
1-6a. The node 1-6a is the boundary node, so that the node 1-1c is
set as the downstream node, and the port connected to the primary
link group 40-ac is set as the downstream port in the routing table
18. Then, the node 1-6a transfers the setting request message to
the node 1-1c. A series of steps as described above is performed in
completely the same manner as performed in the subnetwork 3-a for
the primary path 20-1.
[0187] Next, the node 1-1a sets the routing table 18 for the 21-2
(S23). The node 1-1a selects the same port as allocated to the
21-1, as the downstream port. Then, the node 1-1a generates the
setting response message to the alternate path 21-2 (S24). The
setting request message includes information such as identification
data of the message, identification data indicating that this path
is the alternate path, path number, source node number, destination
node number, route information to the node 1-6a, and upstream port
number of the downstream port, and also information that this path
shares the link with the alternate path 21-1 in the link groups (1,
4), (4, 6).
[0188] The node 1-4a having received the setting request message
selects the same port as allocated to the alternate path 21-1, as
the downstream port for the alternate path 21-2. Further, the node
1-4a writes the port number of the node 1-6a connected to the
downstream port in the setting request message, and transfers it to
the node 1-6a.
[0189] The node 1-6a writes the port indicated from the node 1-4a
by the setting request message in the routing table 18 as the
upstream port. The node 1-6a is the boundary node, so that the same
downstream node and downstream port as set for the primary path
20-2 are set. Then, the node 1-6a transfers the setting request
message to the node 1-1c (S113 to S117 in FIG. 36).
[0190] In this way, setting of the routing table 18 for the primary
path 20-2 and alternate path 21-2 in the subnetwork 3-a is
completed.
[0191] Then, setting for the primary path 20-2 and alternate path
21-2 in the subnetwork 3-c is performed.
[0192] First, the node 1-1c having received the setting request
message to the primary path 20-2 from the node 1-6a (S121 in FIG.
37) calculates the route of the primary path 20-2 from the node
1-1c to node 1-6c (S81 in FIG. 32) and send the route to a
management center 2-c (S82). A centralized control unit 15 of the
management center 2-c records the route in the path table 17 to
prepare a list of a link group not belonging to SRLG that the route
of the primary path 20-2 sent from the node 1-1c pass, and returns
the list to the node 1-1c (S83). Then, the node 1-1c calculates the
route of the alternate path 21-2 from the node 1-1c to node 1-6c
simply using the link groups included in this list (S84). Here, the
contents of the SRLG table or path table in the management center
2-c are the same as in the management center 2-a, so that a
calculation method of the routes of the primary path 20-2 and
alternate path 21-2 in the subnetwork 3-c and the obtained results
are identical to those of the routes of the primary path 20-2 and
alternate path 21-2 in the subnetwork 3-a.
[0193] The node 1-1c also sends the routes of the alternate path
21-2 to the management center 2-c (S85). The management center 2-c
searches for an alternate path having a route overlapping the route
of the alternate path 21-2 in the path table 17, but there is no
such alternate path at this time (N in S87). Thus, the management
center 2-c sends a message indicating "share no resource" to the
node 1-1c, and records the route of the alternate path 21-2 in the
path table 17 (S88).
[0194] Subsequently, the node 1-1c sets the routing table 18 for
the primary path 20-2 (S123 in FIG. 37), and then writes the route
of the primary path 20-2 in the subnetwork 3-c in the setting
request message, and sends it to the node 1-2c. The setting request
message is transferred from the node 1-2c to the node 1-6c (S124).
In accordance therewith, the routing tables 18 for the 20-2 are
also set in the node 1-2c and node 1-6c. The node 1-6c is the
destination node, so that the client is selected as the downstream
node, and the port having the smallest port number is selected from
unused ports connected to the client as the downstream port, and
these are set in the routing table 18. Then, the node 1-6c
generates the setting response message and send it to the node
1-2c. The setting response message is transferred in a direction
opposite the path on the primary path 20-2 to the node 1-1a that is
the source node (S125). In accordance therewith, each node on the
route changes the switch 10 (S126).
[0195] Then, the node 1-1c sets the routing table 18 for the
alternate path 21-2 (S127), and then writes the route of the
alternate path 21-2 in the subnetwork 3-c in the setting request
message, and sends it to the node 1-4c. The setting request message
is transferred from the node 1-4c to the node 1-6c (S128). In
accordance therewith, the routing tables 18 for the alternate path
21-2 are also set in the node 1-4c and node 1-6c, but the link is
not shared with another alternate path. The node 1-6c is the
destination node, so that the client is selected as the downstream
node, and the port having the smallest port number is selected from
unused ports connected to the client as the downstream port, and
these are set in the routing table 18. Then, the node 1-6c
generates the setting response message and send it to the node
1-4c. The setting response message is transferred in a direction
opposite the path on the alternate path 21-2 to the node 1-1a that
is the source node (S129). Each node on the path do not change the
switch 10 when it receives the setting response message to the
alternate path. In this way, setting of the primary path 20-2 and
alternate path 21-2 is completed (S130).
[0196] According to this embodiment, two pairs of path, that is,
the primary path 20-1 and alternate path 21-1, and the primary path
20-2 and alternate path 21-2 can be set so as not to share the SRLG
in each subnetwork 3. Thus, even if failure occurs in the link or
node on the primary path 20-1 or primary path 20-2 in each
subnetwork 3, the failure can be recovered by switching to the
alternate path. At the boundary of each subnetwork 3, failure
recovery is also performed by APS. Further, in the subnetwork 3-a,
the alternate path 21-1 and alternate path 21-2 share the link on
the link groups (1, 4), (4, 6), thereby allowing savings in
alternate sources.
[0197] Next, an eighth embodiment will be described. In the eighth
embodiment, a network consists of a plurality of subnetworks as in
the seventh embodiment, and there is no management center 2. A
configuration of a network is shown in FIG. 22. The configuration
of the network is completely the same as that in the seventh
embodiment except for absence of the management center 2. A
configuration of a node 1 is shown in FIG. 23. In this embodiment,
the node 1 has an external routing table 60 as in the seventh
embodiment. Other than that, the configuration of the node 1 is
completely the same as that in the third embodiment, and includes
an SRLG table 16 and a path table 17.
[0198] Thus, receiving/transmission of messages between the
subnetworks are the same as in the flowcharts of the seventh
embodiment, and operation of the node 1 is the same as in the
flowcharts of the third embodiment. Therefore, description of the
operation using the flowcharts will be omitted in the eighth
embodiment.
[0199] First, setting a primary path 20-1 and alternate path 21-1
whose source is a node 1-1a in a subnetwork 3-a and whose
destination is a node 1-5b in a subnetwork 3-b will be
considered.
[0200] A node control unit 11 of the node 1-1a first refers to the
external routing table 60 to find that a route may pass a node 1-5a
when the path whose destination is the node in the subnetwork 3-b
is set. The node control unit 11 of the node 1-1a refers to a
topology table 12 and the SRLG table 16 to calculate the routes
from the node 1-1a to node 1-5a of the primary path 20-1 and
alternate path 21-1 in the same manner as in the second embodiment.
This provides the routes (1, 3), (3, 5) of the primary path 20-1,
and the routes (1, 4), (4, 6), (5, 6) of the alternate path 21-1,
and these routes share no SRLG. The node 1-1a records the routes
and passing SRLGs in the path table 17.
[0201] Then, the node 1-1a sets a routing table 18 for the primary
path 20-1. A setting manner here is the same as in the seventh
embodiment.
[0202] Next, the node 1-1a sends a setting request message of the
primary path 20-1 that is a kind of signaling messages to the node
1-3a via a control channel 31. The setting request message includes
information such as identification data of the message,
identification data indicating that this path is the primary path,
path number, source node number, destination node number, route
information and SRLG information from the node 1-1a to node 1-5a,
and upstream port number of the downstream port. For the SRLG
information from the node 1-1a to the node 1-5a, all the numbers of
the SRLGs are added to which link groups that this path passes in
the subnetwork 3-a belong. Other than that, the setting request
message is the same as that in the seventh embodiment.
[0203] The node 1-3a having received the setting request message
sets the routing table 18 as in the seventh embodiment, rewrites
the upstream port number of the downstream node in the setting
request message, and sends the setting request message to the node
1-5a. The node 1-3a writes the route information and SRLG
information of the primary path 20-1 indicated by the setting
request message in its own path table 17.
[0204] The node 1-5a having received the setting request message
sets the routing table 18 as in the seventh embodiment, rewrites
the upstream port number of the downstream node in the setting
request message, and sends the setting request message to the node
1-2b. The node 1-5a writes the route information and SRLG
information of the primary path 20-1 indicated by the setting
request message in its own path table 17.
[0205] After setting the primary path 20-1, the node 1-1a sets the
routing table 18 for the alternate path 21-1. At this time, the
node 1-1a refers to the path table 17 and searches for another
alternate path passing the link group (1, 4) like the alternate
path 21-1, but there is no such alternate path. Thus, the node 1-1a
selects the port 10 having the smallest port number from unused
ports connected to the link group (1, 4) as the downstream port,
and writes it in the routing table 18.
[0206] Subsequently, the node 1-1a sends the setting request
message of the alternate path 21-1 to the node 1-4a via the control
channel 31. The setting request message includes information such
as identification data of the message, identification data
indicating that this path is the alternate path, path number,
source node number, destination node number, route information and
SRLG information from the node 1-1a to node 1-5a, and upstream port
number of the downstream port.
[0207] The node 1-4a having received the message refers to the path
table 17 to search for another alternate path passing the link
group (4, 6) like the alternate path 21-1, but there is no such
alternate path. Thus, the node 1-4a selects the port having the
smallest port number from unused ports connected to the link groups
(4, 6) as the downstream port, and writes it in its own routing
table 18. The node 1-4a rewrites the upstream port of the
downstream node of the setting request message, and transfers it to
the node 1-6a. Further, the node 1-4a writes the route information
and SRLG information of the alternate path 21-1 indicated by the
setting request message in its own path table 17.
[0208] The node 1-6a having received the setting request message
refers to the path table 17 to search for another alternate path
passing the link group (5, 6) like the alternate path 21-1, but
there is no such alternate path. Thus, the node 1-6a selects the
port having the smallest port number from unused ports connected to
the link group (5, 6) as the downstream port, and writes it in its
own routing table 18. The node 1-6a rewrites the upstream port of
the downstream node of the setting request message, and transfers
it to the node 1-5a. Further, the node 1-6a writes the route
information and SRLG information of the alternate path 21-1
indicated by the setting request message in its own path table
17.
[0209] The node 1-5a having received the setting request message
knows that the node 1-5a itself is the boundary node, and thus
allocates the same port as allocated to the downstream port of the
alternate path 20-1 to the downstream port of the alternate path
21-1, and sets the routing table 18. The node 1-5a rewrites the
upstream port number of the downstream node of the setting request
message, and transfers it to the node 1-2b. Further, the node 1-5a
writes the route information and SRLG information of the alternate
path 21-1 indicated by the setting request message in its own path
table 17.
[0210] In this way, setting of the routing table 18 for the primary
path 20-1 and alternate path 21-1 in the subnetwork 3-a is
completed.
[0211] On the other hand, the topology table 12 in the subnetwork
3-b stores topology information in the subnetwork 3-b, the contents
of FIG. 4, and information that the node 1-2b is connected to the
node 5a of the subnetwork 3-a. The SRLG table 16 in the subnetwork
3-b holds SRLG information in the subnetwork 3-b, that is, the same
contents as FIG. 5. In the path table 17, routes and SRLGs of the
path in the subnetwork 3-b are recorded.
[0212] In the subnetwork 3-b, the node 1-2b first receives the
setting request message of the primary path 20-1 from the node
1-5a. This message indicates that the destination node of this path
is the node 1-5b in the same subnetwork, but does not indicate the
route thereto. Thus, the node 1-2b refers to the topology table 12
and SRLG table 16 to calculate the routes from the node 1-2b to
node 1-5b of the primary path 20-1 and alternate path 21-1. This
provides the routes (2, 6), (5, 6) of the primary path 20-1, and
the routes (1, 2), (1, 3), (3, 5) of the alternate path 21-1, and
these routes share no SRLG. The node 1-2b records the route and
passing SRLG in the path table 17.
[0213] Then, the node 1-2b sets the routing table 18 for the
primary path 20-1. A setting manner here is the same as in the
seventh embodiment.
[0214] Next, the node 1-2b rewrites the received route information
and SRLG information of the setting request message of the primary
path 20-1 into the route information and SRLG information in the
subnetwork 3-b, and also rewrites the upstream port number of the
downstream node to transmit it to the node 1-6b.
[0215] The node 1-6b having received the setting request message
sets the routing table 18 as in the seventh embodiment, rewrites
the upstream port number of the downstream node in the setting
request message, and send the setting request message to the node
1-5b. The node 1-6b writes the route information and SRLG
information of the primary path 20-1 indicated by the setting
request message in its own path table 17.
[0216] The node 1-5b having received the setting request message
sets the routing table 18 as in the seventh embodiment, changes the
switch 10 in accordance with the contents of the routing table 18,
generates the setting response message, and send it to the node
1-6b. The setting response message is transferred in a direction
opposite the path on the route of the primary path 20-1 to the node
1-1a that is the source node. Each node on the routes receives the
setting response message to change its own switch 10 in accordance
with the contents of the routing table 18. In this way, setting of
the primary path 20-1 is completed.
[0217] Then, the node 1-2b sets the routing table 18 for the
alternate path 21-1. First, the node 1-2b refers to the path table
17 and searches for another alternate path passing the link group
(1, 2) like the alternate path 21-1, but there is no such alternate
path. Thus, the node 1-2b selects the port having the smallest port
number from unused ports connected to the link groups (1, 2) as the
downstream port, and writes it in its own routing table 18. The
node 1-2b rewrites the upstream port of the downstream node of the
setting request message, and transfers it to the node 1-1b.
Further, the node 1-2b writes the route information of the
alternate path 21-1 and SRLG information indicated by the setting
request message in its own path table 17.
[0218] The node 1-1b having received the setting, request message
refers to the path table 17 to search for another alternate path
passing the link group (1, 3) like the alternate path 21-1, but
there is no such alternate path. Thus, the node 1-1b selects the
port having the smallest port number from unused ports connected to
the link groups (1, 3) as the downstream port, and writes it in its
own routing table 18. The node 1-1b rewrites the upstream port of
the downstream node of the setting request message, and transfers
it to the node 1-3b. Further, the node 1-1b writes the route
information and SRLG information of the alternate path 21-1
indicated by the setting request message in its own path table
17.
[0219] The node 1-3b having received the setting request message
refers to the path table 17 to search for another alternate path
passing a link group (3, 5) like the alternate path 21-1, but there
is no such alternate path. Thus, the node 1-3b selects the port
having the smallest port number from unused ports connected to the
link groups (3, 5) as the downstream port, and writes it in its own
routing table 18. The node 1-3b rewrites the upstream port of the
downstream node of the setting request message, and transfers it to
the node 1-5b. Further, the node 1-3b writes the route information
and SRLG information of the alternate path 21-1 indicated by the
setting request message in its own path table 17.
[0220] The node 1-5b having received the setting request message is
the destination node of the alternate path 21-1, and thus allocates
the same port as allocated to the downstream port of the primary
path 20-1 to the downstream port of the alternate path 21-1, and
sets the routing table 18. Then, the node 1-5b generates the
setting response message, and send it to the node 1-3b. The setting
response message is transferred in a direction opposite the path on
the route of the alternate path 21-1 to the node 1-1a that is the
source node. This setting response message is for the alternate
path, and thus each node on the route does not change the switch
10. In this way, setting of the alternate path 21-1 is
completed.
[0221] Next, setting a primary path 20-2 and alternate path 21-2
whose source is the node 1-1a in subnetwork 3-a and whose
destination is a node 1-6c in a subnetwork 3-c will be
considered.
[0222] The node control unit 11 of the node 1-1a first refers to
the external routing table 60 to find that the route may pass the
node 1-6a when the path whose destination is the node in the
subnetwork 3-c is set. The node control unit 11 of the node 1-1a
refers to the topology table 12 and SRLG table 16 to calculate the
routes from the node 1-1a to node 1-6a of the primary path 20-2 and
alternate path 21-2 in the same manner as in the second embodiment.
This provides the routes (1, 2), (2, 6) of the primary path 20-2,
and the routes (1, 4), (4, 6) of the alternate path 21-2, and these
routes share no SRLG. The node 1-1a records the routes and passing
SRLGs in the path table 17.
[0223] Then, the node 1-1a sets the routing table 18 for the
primary path 20-2, and generates the setting request message of the
primary path 20-2. The setting request message is transferred from
the node 1-1a to node 1-2a, and node 1-6a, and in accordance
therewith, the routing table 18 is set, and the route information
and SRLG information are written in the path table 17 also in the
node 1-2a and node 1-6a. The node 1-6a that is the boundary node
selects the port connected to the link group 40-ac as the
downstream port, and transfers the setting request message to the
node 1-1c. The above described steps are performed in completely
the same manner as for the primary path 20-1 in the subnetwork
3-a.
[0224] Then, the node 1-1a sets the routing table 18 for the
alternate path 21-2. First, the node 1-1a searches the path table
17 and checks whether there is another alternate path passing the
link group (1, 4). The alternate path 21-1 applies thereto here, so
that the node 1-1a compares the SRLGs in the subnetwork 3-a that
the primary path 20-1 and primary path 20-2 pass. The comparison
reveals that both SRLGs do not overlap, and thus the node 1-1a
selects the same port as allocated to the alternate path 21-1, as
the downstream port of the alternate path 21-2. That is, the two
alternate paths share the link in the link group (1, 4). Then, the
node 1-1a generates the setting request message of the alternate
path 21-2 and sends it to the node 1-4a. This setting request
message includes the paths information and SRLG information of the
alternate path 21-2 in the subnetwork 3-a.
[0225] The node 1-4a having received the setting request message
searches its own path table 17 and checks whether there is another
alternate path passing the link group (4, 6). The alternate path
21-1 also applies thereto here, so that the node 1-4a compares the
SRLGs in the subnetwork 3-a that the primary path 20-1 and primary
path 20-2 pass. Both SRLGs do not overlap, so that the node 1-4a
selects the same port as allocated to the alternate path 21-1, as
the downstream port of the alternate path 21-2. That is, the two
alternate paths share the link also in the link group (4, 6). The
node 1-4a writes the paths information and SRLG information of the
alternate path 21-2 indicated by the setting request message in its
own path table 17.
[0226] The node 1-6a having received the setting request message is
the boundary node, and thus selects the same port as allocated to
the primary path 20-2, as the downstream port of the alternate path
21-2, and sets it in the routing table 18. The node 1-6a writes the
paths information and SRLG information of the alternate path 21-2
indicated by the setting request message in its own path table 17.
Further, the node 1-6a rewrites the upstream port of the downstream
node in the setting request message, and transfers it to the node
1-1c.
[0227] In this way, setting of the routing table 18 for the primary
path 20-2 and alternate path 21-2 in the subnetwork 3-a is
completed.
[0228] On the other hand, in the subnetwork 3-c, the node 1-1c
receives the setting request message of the primary path 20-2 from
the node 1-6a. This message indicates that the destination node of
this path is the node 1-6c in the same subnetwork, but does not
indicate the route thereto. Thus, the node 1-1c refers to the
topology table 12 and SRLG table 16 to calculate the routes from
the node 1-1c to node 1-6c of the primary path 20-2 and alternate
path 21-2. This provides the routes (1, 2), (2, 6) of the primary
path 20-2, and the routes (1, 4), (4, 6) of the alternate path
21-2, and these routes share no SRLG. The node 1-1c records the
routes and passing SRLGs in the path table 17.
[0229] Then, the node 1-1c sets the routing table 18 for the
primary path 20-2, and generates the setting request message. The
setting request message is transferred from the node 1-1c to the
node 1-2c and node 1-6c, and in accordance therewith, the routing
table 18 is set, and the route information and SRLG information are
written in the path table 17 also in the node 1-2c and node 1-6c.
The node 1-6c is the destination node, and when setting the routing
table 18, the node 1-6c changes the switch 10 in accordance
therewith to generate the setting response message. The setting
response message is transferred in a direction opposite the path on
the route of the primary path 20-2 to the node 1-1a that is the
source node. Each node on the route receives the setting response
message to change its own switch 10 in accordance with the contents
of the routing table 18. The above described steps are performed in
completely the same manner as for the primary path 20-1 in the
subnetwork 3-b. Therefore, setting of the primary path 20-2 is
completed.
[0230] Then, the node 1-1c sets the routing table 18 for the
alternate path 21-2. First, the node 1-1c refers to the path table
17 and searches for another alternate path passing a link group (1,
4) like the alternate path 21-2, but there is no such alternate
path. Thus, the node 1-1c selects the port having the smallest port
number from unused ports connected to the link group (1, 4) as the
downstream port, and writes it in its own routing table 18. The
node 1-1c rewrites the upstream port of the downstream node of the
setting request message, and transfers it to the node 1-4c.
Further, the node 1-1c writes the route information and SRLG
information of the alternate path 21-2 indicated by the setting
request message in its own path table 17.
[0231] The node 1-4c having received the setting request message
refers to the path table 17 to search for another alternate path
passing the link group (4, 6) like the alternate path 21-2, but
there is no such alternate path. Thus, the node 1-4c selects the
port having the smallest port number from unused ports connected to
the link group (4, 6) as the downstream port, and writes it in its
own routing table 18. The node 1-4c rewrites the upstream port of
the downstream node of the setting request message, and transfers
it to the node 1-6c. Further, the node 1-4c writes the route
information and SRLG information of the alternate path 21-2
indicated by the setting request message in its own path table
17.
[0232] The node 1-6c having received the setting request message is
the destination node of the alternate path 21-2, and thus allocates
the same port as allocated to the downstream port of the primary
path 20-2 to the downstream port of the alternate path 21-2, and
sets the routing table 18. Then, the node 1-6c generates the
setting response message, and send it to the node 1-3c. The setting
response message is transferred in a direction opposite the path on
the route of the alternate path 21-2 to the node 1-1a that is the
source node. This setting response message is for the alternate
path, and thus each node on the route does not change the switch
10. In this way, setting of the alternate path 21-2 is
completed.
[0233] According to this embodiment, two pairs of path, that is the
primary path 20-1 and alternate path 21-1, and the primary path
20-2 and alternate path 21-2 can be set so as not to share the SRLG
in each subnetwork 3. Thus, even if failure occurs in the link or
node on the primary path 20-1 or primary path 20-2 in each
subnetwork 3, the failure can be recovered by switching to the
alternate path. At the boundary of each subnetwork 3, failure
recovery is also performed by APS. Further, in the subnetwork 3-a,
the alternate path 21-1 and alternate path 21-2 shares the link on
the link groups (1, 4), (4, 6), thereby allowing savings in
alternate sources.
[0234] In this embodiment, the above described advantages are
obtained by decentralized control without centralized controlling
means.
[0235] The present invention can be applied to the embodiments
described below.
[0236] 1. In the above described embodiments, the two-way link is
used, but a one-way way link may be used.
[0237] 2. It is described that there are a plurality of links as a
link group, but not limited to the plurality of links, there may be
a single link.
[0238] 3. In the above described embodiments, a path setting method
in consideration of SRLG as a risk sharing group is described, but
the risk sharing group is not limited to the SRLG. For example, a
path setting method in consideration of a risk sharing group such
as "a group of nodes sharing a resource" may be possible.
[0239] 4. In the above described embodiment, a method for setting
the primary path and alternate path between two nodes is described,
but differentiation between the primary path and alternate path is
not always necessary. For example, both two paths may be primary
paths and used for load decentralization (applicable to the fifth
embodiment).
[0240] 5. In the above described embodiments, it is described that
the source nodes of the plurality of primary and alternate paths
that share the alternate resource (link) are the same, but not
limited to this, the paths may be set in similar steps when, for
example, a source node of a first pair of primary and alternate
paths are a node 1-1, and a source node of a second pair of primary
and alternate paths are a node 1-2.
[0241] 6. In the above described embodiments, there are two pairs
of primary and alternate paths that share the alternate resource
(link), but not limited to this, there maybe three or more pairs.
Setting steps in that case are the same as those of the first pairs
of paths and the second pairs of paths (though the results are
different due to the different conditions). For example, repeating
the steps for five pairs, five pairs of primary and alternate paths
may share the alternate resource.
[0242] As described above, in the seventh and eight embodiments,
signaling of the setting request message is performed from the
source node via the midstream nodes to the destination node, and
after the routing table is set in the destination node, the setting
response message is transferred from the destination node to the
source node on the same route in the opposite direction. Each node
on the route receives the setting response message, changes its own
switch in accordance with the contents of the routing table, and in
this way, setting of the primary and alternate paths is completed
(for the seventh embodiment, see page 46, lines 1 to 21, and page
47, lines 5 to 14, and for the eighth embodiment, see page 58,
lines 17 to 27, page 60, lines 10 to 22, page 63, line 18 to page
64, line 7, and page 65, lines 5 to 17).
[0243] In the first to sixth embodiments, described steps are
signaling of the setting request message from the source node via
the midstream nodes to the destination node, and setting of the
routing table in the destination node, for convenience of
explanation. However, actually, after the routing table is set in
the destination node, the setting response message is transferred
from the destination node to the source node on the same route in
the opposite direction as in the seventh and eighth
embodiments.
[0244] Next, a ninth embodiment will be described. The ninth
embodiment relates to a recording medium having a path setting
program recorded thereon. The path setting program is a program to
perform steps shown in the flowcharts of FIGS. 24 to 38 in a
computer. Each step of the flowchart with indication of (N) at its
front is a node control program, and each step with indication of
(K) is a management center control program. These programs are
recorded in the recording medium.
[0245] Then, a configuration of a unit controlled by the path
setting program will be described. FIG. 39 shows a configuration of
a node controlled by the path setting program, and FIG. 40 shows a
configuration of a management center controlled by the path setting
program.
[0246] First, a configuration of the node will be described. With
reference to FIG. 39, a node 1 comprises a CPU (central processing
unit) 101 in addition to a node control unit 11. The CPU 101 reads
a program from a recording medium having a path setting program
recorded thereon 102N, and controls the node control unit 11 in the
node 1. The contents of control is described above, and the
description thereof will be omitted.
[0247] Next, a configuration of the management center will be
described. With reference to FIG. 40, the management center 2
comprises a CPU 103 in addition to a centralized control unit 15.
The CPU 103 reads a program from a recording medium having a path
setting program recorded thereon 102K, and controls the centralized
control unit 15 in the management center 2. The contents of control
are also described above, and the description thereof will be
omitted.
[0248] The first aspect of the invention provides a communication
network including a plurality of nodes constituting a network and a
management center connected to each of the nodes, wherein each of
the nodes has topology information of the network, and the
management center has information on a risk sharing resource group,
thereby allowing load of route calculation to be decentralized to
the nodes and the management center. This prevents the load of the
route calculation from being centralized in part of units and
prevents increase in traffic between the nodes.
[0249] The second to sixth aspects of the invention achieves the
same advantages as the first aspect. Further, advantages obtained
from each embodiment are summarized as described below.
[0250] In the first and fourth embodiments, each of the nodes has
topology information of the network, and the management center has
information on the risk sharing resource group and currently set
path information, so that each node no longer needs to hold the
information on the risk sharing source and path information.
Therefore, load on each node can be reduced.
[0251] In the first embodiment, information on whether SRLGs
overlap is obtained from the management center after routes of the
primary and alternate paths are calculated, so that several times
of calculation is sometimes required before the primary and
alternate paths having no overlapping SRLG can be obtained.
However, in the fourth embodiment, a list of SRLGs not included in
the route of the primary path is received from the management
center before the route of the alternate path is calculated,
thereby always allowing single calculation of the alternate
path.
[0252] In the second embodiment, each node has topology information
of the network and information on the risk sharing resource group,
and the management center has currently set path information, so
that each node no longer needs to hold the path information.
Therefore, load on each node can be reduced.
[0253] In the third embodiment, each node has topology information
of the network, information on the risk sharing resource group, and
information on a currently set path passing the node itself,
thereby eliminating the need for the management center, and
preventing the number of nodes of the network from being limited by
capacity of the management center. Failure of the management center
do not cause the entire network to be down. Further, each node
holds only information on the path passing the node itself as path
information, so that a large memory for each node is not required.
Also, each node searches for only existing alternate paths having
the overlapping route in the link group between the node itself and
the downstream node, thereby allowing load of searching for an
existing path on each node to be reduced.
[0254] In the fifth embodiment, each node has topology information
of the network, and the management center has information on the
risk sharing resource group, so that each node no longer needs to
hold the information on the risk sharing resource group. Therefore,
load on each node can be reduced.
[0255] In the sixth embodiment, each node has topology information
of the network, and the management center has currently set path
information, so that each node no longer needs to hold the path
information. Therefore, load on each node can be reduced.
[0256] In the seventh and eighth embodiments, the network shown in
the first to sixth embodiments consists of a plurality of
subnetworks, thereby allowing the primary path and alternate path
closed for each subnetwork to be set. Therefore, failure recovery
is performed for each subnetwork, and failure recovery time is
reduced.
* * * * *